This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 6 |
| 3 | 30 |
| 4 | 186 |
| 5 | 1140 |
| 6 | 7116 |
| 7 | 44856 |
| 8 | 285066 |
| 9 | 1823232 |
| 10 | 11721726 |
| 11 | 75683718 |
| 12 | 490429224 |
| 13 | 3187723344 |
| 14 | 20774505408 |
| 15 | 135699314640 |
| 16 | 888177411018 |
| 17 | 5823660624408 |
| 18 | 38245666664994 |
| 19 | 251528316024042 |
| 20 | 1656338630258826 |
| 21 | 10919849458481028 |
| 22 | 72068276593960884 |
| 23 | 476093333668519872 |