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 | 1 |
| 2 | 4 |
| 3 | 3 |
| 4 | 144 |
| 5 | 40 |
| 6 | 4320 |
| 7 | 1260 |
| 8 | 134400 |
| 9 | 72576 |
| 10 | 21772800 |
| 11 | 6652800 |
| 12 | 100590336000 |
| 13 | 889574400 |
| 14 | 34871316480 |
| 15 | 163459296000 |
| 16 | 627683696640000 |
| 17 | 39520825344000 |
| 18 | 268899695640576000 |
| 19 | 12164510040883200 |
| 20 | 38231317271347200000 |
| 21 | 4644631106519040000 |
| 22 | 6744004366665646080000 |