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 | 0 |
| 2 | -2 |
| 3 | -3 |
| 4 | 4 |
| 5 | 30 |
| 6 | 66 |
| 7 | 0 |
| 8 | -496 |
| 9 | -1512 |
| 10 | 1800 |
| 11 | 51480 |
| 12 | 487752 |
| 13 | 4633200 |
| 14 | 50605296 |
| 15 | 620703720 |
| 16 | 8278947840 |
| 17 | 118504008000 |
| 18 | 1811156124096 |
| 19 | 29452505385600 |
| 20 | 507926275873920 |
| 21 | 9260774050469760 |
| 22 | 178004846331607680 |
| 23 | 3597786477984061440 |
| 24 | 76284908749415574144 |
| 25 | 1693206585883612800000 |
| 26 | 39264054809925638534400 |