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 | 10 |
| 3 | 252 |
| 4 | 12176 |
| 5 | 966240 |
| 6 | 114341760 |
| 7 | 18897709824 |
| 8 | 4160840140800 |
| 9 | 1177736213606400 |
| 10 | 416807049369600000 |
| 11 | 180368555623280640000 |
| 12 | 93711488655948742656000 |
| 13 | 57572391079539343687680000 |