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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 240 |
| 6 | 2040 |
| 7 | 17640 |
| 8 | 162456 |
| 9 | 1614816 |
| 10 | 17368320 |
| 11 | 201828000 |
| 12 | 2526193824 |
| 13 | 33936357312 |
| 14 | 487530074304 |
| 15 | 7463742249600 |
| 16 | 121367896891776 |
| 17 | 2089865973021696 |
| 18 | 37999535417459712 |
| 19 | 727710096185266176 |
| 20 | 14642785817771802624 |
| 21 | 308902349883623731200 |
| 22 | 6818239581643475251200 |