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 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 5020 |
| 8 | 40000 |
| 9 | 358560 |
| 10 | 3571200 |
| 11 | 39124800 |
| 12 | 467612575 |
| 13 | 6054492822 |
| 14 | 84421683166 |
| 15 | 1261227594360 |
| 16 | 20098408531680 |
| 17 | 340297488208325 |
| 18 | 6100696794591542 |
| 19 | 115446620042888642 |
| 20 | 2299637587367422120 |
| 21 | 48097983978364729800 |
| 22 | 1053895947990450296810 |