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 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 10 |
| 6 | 120 |
| 7 | 105 |
| 8 | 336 |
| 9 | 2268 |
| 10 | 15120 |
| 11 | 332640 |
| 12 | 498960 |
| 13 | 6486480 |
| 14 | 43243200 |
| 15 | 259459200 |
| 16 | 3113510400 |
| 17 | 35286451200 |
| 18 | 1270312243200 |
| 19 | 3016991577600 |
| 20 | 60339831552000 |
| 21 | 1267136462592000 |
| 22 | 37169336236032000 |
| 23 | 160292762517888000 |