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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 0 |
| 5 | -4 |
| 6 | -10 |
| 7 | 15 |
| 8 | 210 |
| 9 | 504 |
| 10 | -3528 |
| 11 | -34440 |
| 12 | -36960 |
| 13 | 1512720 |
| 14 | 11763180 |
| 15 | -24549525 |
| 16 | -1118467350 |
| 17 | -6466860400 |
| 18 | 62185563440 |
| 19 | 1297024576848 |
| 20 | 3903558763104 |
| 21 | -149417396724960 |
| 22 | -2150022118411440 |
| 23 | 3233834859735480 |
| 24 | 449839942314082320 |