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 | 0 |
| 2 | 6 |
| 3 | 9 |
| 4 | 96 |
| 5 | 450 |
| 6 | 3132 |
| 7 | 22680 |
| 8 | 179904 |
| 9 | 1578528 |
| 10 | 15282000 |
| 11 | 162304560 |
| 12 | 1879227072 |
| 13 | 23579281440 |
| 14 | 318874800384 |
| 15 | 4625170411680 |
| 16 | 71640771563520 |
| 17 | 1180394962790400 |
| 18 | 20616532017767424 |
| 19 | 380509312545031680 |
| 20 | 7400308896979660800 |
| 21 | 151271976281858611200 |
| 22 | 3242509236999683481600 |