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 | 1 |
| 3 | 0 |
| 4 | 12 |
| 5 | 132 |
| 6 | 540 |
| 7 | 0 |
| 8 | 20160 |
| 9 | 423360 |
| 10 | 8164800 |
| 11 | 125193600 |
| 12 | 1172102400 |
| 13 | 11935123200 |
| 14 | 76281004800 |
| 15 | 0 |
| 16 | 10461394944000 |
| 17 | 428917192704000 |
| 18 | 14781951055872000 |
| 19 | 429147343392768000 |
| 20 | 14090871305871360000 |
| 21 | 461146030563778560000 |
| 22 | 13730871481551544320000 |
| 23 | 390084405122331279360000 |