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 | 21 |
| 3 | 85 |
| 4 | 365 |
| 5 | -5707 |
| 6 | -24935 |
| 7 | -108872 |
| 8 | 1713705 |
| 9 | 7480420 |
| 10 | 32652893 |
| 11 | -513913649 |
| 12 | -2243303605 |
| 13 | -9792325686 |
| 14 | 154118686736 |
| 15 | 672748988550 |
| 16 | 2936640671285 |
| 17 | -46218967738367 |
| 18 | -201752069488280 |
| 19 | -880675175822422 |
| 20 | 13860700755359325 |
| 21 | 60503840705600655 |
| 22 | 264107479466296733 |