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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 15 |
| 5 | 240 |
| 6 | 2604 |
| 7 | 24180 |
| 8 | 207732 |
| 9 | 1710108 |
| 10 | 13739550 |
| 11 | 108853512 |
| 12 | 855732465 |
| 13 | 6700902804 |
| 14 | 52395480996 |
| 15 | 409733313444 |
| 16 | 3207687963129 |
| 17 | 25155951725808 |
| 18 | 197703130100532 |
| 19 | 1557413160706764 |
| 20 | 12298597436673711 |
| 21 | 97359729090421320 |
| 22 | 772615510913274126 |
| 23 | 6145842794363133324 |