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 | 24 |
| 5 | 240 |
| 6 | 1560 |
| 7 | 8400 |
| 8 | 40800 |
| 9 | 186480 |
| 10 | 818280 |
| 11 | 3498000 |
| 12 | 14674440 |
| 13 | 60780720 |
| 14 | 249393480 |
| 15 | 1016542560 |
| 16 | 4123132800 |
| 17 | 16664094960 |
| 18 | 67171179600 |
| 19 | 270232006800 |
| 20 | 1085569963080 |
| 21 | 4356217672800 |
| 22 | 17466683473800 |