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) |
|---|---|
| 3 | 0 |
| 4 | 3 |
| 5 | 28 |
| 6 | 250 |
| 7 | 1760 |
| 8 | 12502 |
| 9 | 82880 |
| 10 | 576060 |
| 11 | 4200960 |
| 12 | 29987760 |
| 13 | 239978112 |
| 14 | 1744142400 |
| 15 | 15361632000 |
| 16 | 119854864800 |
| 17 | 1159352230400 |
| 18 | 9698664271680 |
| 19 | 103688467983360 |
| 20 | 906866458156800 |
| 21 | 10282952826685440 |
| 22 | 97685444140416000 |
| 23 | 1224926383944806400 |
| 24 | 11906083013106585600 |