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 | 0 |
| 3 | -64 |
| 4 | 665 |
| 5 | -14960 |
| 6 | 247184 |
| 7 | -4579625 |
| 8 | 81186496 |
| 9 | -1463617920 |
| 10 | 26217022705 |
| 11 | -470764268256 |
| 12 | 8445336180000 |
| 13 | -151560390359569 |
| 14 | 2719538168853120 |
| 15 | -48800836192146880 |
| 16 | 875690649999921929 |
| 17 | -15713664197268146000 |
| 18 | 281970036429821245616 |
| 19 | -5059748557502924705465 |
| 20 | 90793493265349521060160 |
| 21 | -1629223203785737022267136 |
| 22 | 29235223670642547226470625 |