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 | 0 |
| 5 | 120 |
| 6 | 6912 |
| 7 | 52920 |
| 8 | 466944 |
| 9 | 1905120 |
| 10 | 8647680 |
| 11 | 25613280 |
| 12 | 81838080 |
| 13 | 198764280 |
| 14 | 510478080 |
| 15 | 1082161080 |
| 16 | 2393997312 |
| 17 | 4594961280 |
| 18 | 9120190464 |
| 19 | 16225246080 |
| 20 | 29656350720 |
| 21 | 49689816120 |
| 22 | 85128088320 |
| 23 | 135870624120 |