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 | -8 |
| 3 | -46 |
| 4 | 64 |
| 5 | 7280 |
| 6 | 118720 |
| 7 | 406160 |
| 8 | -35578880 |
| 9 | -1156775680 |
| 10 | -12796467200 |
| 11 | 444964083200 |
| 12 | 27457634713600 |
| 13 | 594958346547200 |
| 14 | -9096689344716800 |
| 15 | -1258068242084608000 |
| 16 | -45330583283597312000 |
| 17 | 24150498582339584000 |
| 18 | 95678058298287259648000 |
| 19 | 5379182782796767182848000 |