Differentiating Arctan(x)

It's great fun to differentiate Arctan(x)! Here are the first 20 derivatives. (Notice that where n represents the number of the derivatives and t represents the number of terms in the expression, as n->infinity, t->infinity.) I would have done more, but I have limited diskquota.
Derivative                      Differentiation

                                       1
1.                                   ------
                                          2
                                     1 + x


                                         x
2.                               - 2 ---------
                                           2 2
                                     (1 + x )


                                   2
                                  x           2
3                           8 --------- - ---------
                                    2 3         2 2
                              (1 + x )    (1 + x )


                                   3
                                  x              x
4.                       - 48 --------- + 24 ---------
                                    2 4            2 3
                              (1 + x )       (1 + x )


                            4               2
                           x               x           24
5.                 384 --------- - 288 --------- + ---------
                             2 5             2 4         2 3
                       (1 + x )        (1 + x )    (1 + x )


                           5                3
                          x                x               x
6.             - 3840 --------- + 3840 --------- - 720 ---------
                            2 6              2 5             2 4
                      (1 + x )         (1 + x )        (1 + x )


                   6                 4                 2
                  x                 x                 x          720
7.      46080 --------- - 57600 --------- + 17280 --------- - ---------
                    2 7               2 6               2 5         2 4
              (1 + x )          (1 + x )          (1 + x )    (1 + x )


                 7                  5                  3
                x                  x                  x                 x
8. - 645120 --------- + 967680 --------- - 403200 --------- + 40320 ---------
                  2 8                2 7                2 6               2 5
            (1 + x )           (1 + x )           (1 + x )          (1 + x )


9.            8                    6                   4                   2
             x                    x                   x                   x
10321920 --------- - 18063360 --------- + 9676800 --------- - 1612800 ---------
               2 9                  2 8                 2 7                 2 6
         (1 + x )             (1 + x )            (1 + x )            (1 + x )

         40320
     + ---------
             2 5
       (1 + x )


10.                     9                      7                     5
                       x                      x                     x
       - 185794560 ---------- + 371589120 --------- - 243855360 ---------
                         2 10                   2 9                   2 8
                   (1 + x )               (1 + x )              (1 + x )

                            3
                           x                   x
            + 58060800 --------- - 3628800 ---------
                             2 7                 2 6
                       (1 + x )            (1 + x )


11.                   10                      8                       6
                     x                       x                       x
      3715891200 ---------- - 8360755200 ---------- + 6502809600 ---------
                       2 11                    2 10                    2 9
                 (1 + x )                (1 + x )                (1 + x )

                             4                     2
                            x                     x        3628800
           - 2032128000 --------- + 217728000 --------- - ---------
                              2 8                   2 7         2 6
                        (1 + x )              (1 + x )    (1 + x )


12.                  11                        9                         7
                    x                         x                         x
  - 81749606400 ---------- + 204374016000 ---------- - 183936614400 ----------
                      2 12                      2 11                      2 10
                (1 + x )                  (1 + x )                  (1 + x )

                          5                       3
                         x                       x                     x
       + 71530905600 --------- - 11176704000 --------- + 479001600 ---------
                           2 9                     2 8                   2 7
                     (1 + x )                (1 + x )              (1 + x )


13.                 12                         10                         8
                   x                          x                          x
 1961990553600 ---------- - 5395474022400 ---------- + 5518098432000 ----------
                     2 13                       2 12                       2 11
               (1 + x )                   (1 + x )                   (1 + x )

                           6                         4
                          x                         x
      - 2575112601600 ---------- + 536481792000 ---------
                            2 10                      2 9
                      (1 + x )                  (1 + x )

                         2
                        x       479001600
      - 40236134400 --------- + ---------
                          2 8         2 7
                    (1 + x )    (1 + x )


14.                            13                           11
                              x                            x
         - 51011754393600 ---------- + 153035263180800 ----------
                                2 14                         2 13
                          (1 + x )                     (1 + x )

                                     9                           7
                                    x                           x
              - 175352905728000 ---------- + 95647039488000 ----------
                                      2 12                        2 11
                                (1 + x )                    (1 + x )

                                    5                          3
                                   x                          x
              - 25107347865600 ---------- + 2789705318400 ---------
                                     2 10                       2 9
                               (1 + x )                   (1 + x )

                                x
              - 87178291200 ---------
                                  2 8
                            (1 + x )


15.                           14                            12
                             x                             x
        1428329123020800 ---------- - 4642069649817600 ----------
                               2 15                          2 14
                         (1 + x )                      (1 + x )

                                     10                            8
                                    x                             x
             + 5891857632460800 ---------- - 3682411020288000 ----------
                                      2 13                          2 12
                                (1 + x )                      (1 + x )

                                     6                            4
                                    x                            x
             + 1171676233728000 ---------- - 175751435059200 ----------
                                      2 11                         2 10
                                (1 + x )                     (1 + x )

                                  2
                                 x       87178291200
             + 9763968614400 --------- - -----------
                                   2 9          2 8
                             (1 + x )     (1 + x )


16.                            15                              13
                              x                               x
      - 42849873690624000 ---------- + 149974557917184000 ----------
                                2 16                            2 15
                          (1 + x )                        (1 + x )

                                     11                              9
                                    x                               x
           - 208893134241792000 ---------- + 147296440811520000 ----------
                                      2 14                            2 13
                                (1 + x )                        (1 + x )

                                    7                              5
                                   x                              x
           - 55236165304320000 ---------- + 10545086103552000 ----------
                                     2 12                           2 11
                               (1 + x )                       (1 + x )

                                  3
                                 x                           x
           - 878757175296000 ---------- + 20922789888000 ---------
                                   2 10                        2 9
                             (1 + x )                    (1 + x )


17.                           16                               14
                             x                                x
     1371195958099968000 ---------- - 5141984842874880000 ----------
                               2 17                             2 16
                         (1 + x )                         (1 + x )

                                     12                               10
                                    x                                x
          + 7798677011693568000 ---------- - 6127531937759232000 ----------
                                      2 15                             2 14
                                (1 + x )                         (1 + x )

                                     8                               6
                                    x                               x
          + 2651335934607360000 ---------- - 618645051408384000 ----------
                                      2 13                            2 12
                                (1 + x )                        (1 + x )

                                   4                             2
                                  x                             x
          + 70300574023680000 ---------- - 3012881743872000 ----------
                                    2 11                          2 10
                              (1 + x )                      (1 + x )

            20922789888000
          + --------------
                     2 9
               (1 + x )


18.                            17                                 15
                              x                                  x
   - 46620662575398912000 ---------- + 186482650301595648000 ----------
                                2 18                               2 17
                          (1 + x )                           (1 + x )

                                     13                                 11
                                    x                                  x
        - 305948098151055360000 ---------- + 265155018397581312000 ----------
                                      2 16                               2 15
                                (1 + x )                           (1 + x )

                                     9                                 7
                                    x                                 x
        - 130210053677383680000 ---------- + 36058168710660096000 ----------
                                      2 14                              2 13
                                (1 + x )                          (1 + x )

                                   5                               3
                                  x                               x
        - 5258482936971264000 ---------- + 341459930972160000 ----------
                                    2 12                            2 11
                              (1 + x )                        (1 + x )

                                x
        - 6402373705728000 ----------
                                 2 10
                           (1 + x )


19.                          18                                  16
                            x                                   x
 1678343852714360832000 ---------- - 7132961374036033536000 ----------
                              2 19                                2 18
                        (1 + x )                            (1 + x )

                                     14                                   12
                                    x                                    x
      + 12587578895357706240000 ---------- - 11931975827891159040000 ----------
                                      2 17                                 2 16
                                (1 + x )                             (1 + x )

                                    10                                  8
                                   x                                   x
      + 6562586705340137472000 ---------- - 2109402869573615616000 ----------
                                     2 15                                2 14
                               (1 + x )                            (1 + x )

                                   6                                 4
                                  x                                 x
      + 378610771461931008000 ---------- - 33804533166243840000 ----------
                                    2 13                              2 12
                              (1 + x )                          (1 + x )

                                 2
                                x        6402373705728000
      + 1152427267031040000 ---------- - ----------------
                                  2 11            2 10
                            (1 + x )        (1 + x )


20.                            19                                    17
                              x                                     x
- 63777066403145711616000 ---------- + 286996798814155702272000 ----------
                                2 20                                  2 19
                          (1 + x )                              (1 + x )

                                     15
                                    x
     - 542105064426738548736000 ----------
                                      2 18
                                (1 + x )

                                     13
                                    x
     + 558049331027524976640000 ----------
                                      2 17
                                (1 + x )

                                     11
                                    x
     - 340061311094898032640000 ----------
                                      2 16
                                (1 + x )

                                     9                                    7
                                    x                                    x
     + 124689147401462611968000 ---------- - 26719103014599131136000 ----------
                                      2 15                                 2 14
                                (1 + x )                             (1 + x )

                                   5                                  3
                                  x                                  x
     + 3082973424761438208000 ---------- - 160571532539658240000 ----------
                                    2 13                               2 12
                              (1 + x )                           (1 + x )

                                x
     + 2432902008176640000 ----------
                                 2 11
                           (1 + x )
See if you can work out the 21st derivative!
Last modified on Feb 21, 1998 by Jason Hildebrand
(jason@alumni.uwaterloo.ca)