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 | 1 |
| 2 | -1 |
| 3 | 0 |
| 4 | 9 |
| 5 | -48 |
| 6 | 15 |
| 7 | 2448 |
| 8 | -24927 |
| 9 | 23424 |
| 10 | 3091311 |
| 11 | -47659200 |
| 12 | 88056969 |
| 13 | 10702667520 |
| 14 | -225139993377 |
| 15 | 679791291648 |
| 16 | 78646340795265 |
| 17 | -2128005345251328 |
| 18 | 9456106738649631 |
| 19 | 1053535684549174272 |