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 | 0 |
| 2 | 2 |
| 3 | -6 |
| 4 | 12 |
| 5 | 200 |
| 6 | -6240 |
| 7 | 139440 |
| 8 | -2869440 |
| 9 | 53386560 |
| 10 | -708048000 |
| 11 | -6667689600 |
| 12 | 1162101600000 |
| 13 | -68789252563200 |
| 14 | 3158414682259200 |
| 15 | -118988867559744000 |
| 16 | 3123174474201600000 |
| 17 | 17680394964750336000 |
| 18 | -10490102782572441600000 |