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 | 3 |
| 4 | 8 |
| 5 | 15 |
| 6 | 144 |
| 7 | 420 |
| 8 | 5760 |
| 9 | 4536 |
| 10 | 403200 |
| 11 | 1995840 |
| 12 | 6220800 |
| 13 | 259459200 |
| 14 | 1341204480 |
| 15 | 46702656000 |
| 16 | 1394852659200 |
| 17 | 11115232128000 |
| 18 | 376610217984000 |
| 19 | 96543730483200 |
| 20 | 128047474114560000 |
| 21 | 1277273554292736000 |