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 | 467596800 |
| 13 | 6054250840 |
| 14 | 84417778720 |
| 15 | 1261161277200 |
| 16 | 20097223449600 |
| 17 | 340275330912000 |
| 18 | 6100262355686400 |
| 19 | 115437689217984148 |
| 20 | 2299445555596421920 |
| 21 | 48093671993708346480 |
| 22 | 1053794989665442654080 |