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 | 0 |
| 3 | 0 |
| 4 | 12 |
| 5 | 60 |
| 6 | 240 |
| 7 | 1680 |
| 8 | 15120 |
| 9 | 136080 |
| 10 | 1330560 |
| 11 | 14636160 |
| 12 | 176299200 |
| 13 | 2291889600 |
| 14 | 32069157120 |
| 15 | 481037356800 |
| 16 | 7697116627200 |
| 17 | 130850982662400 |
| 18 | 2355300044697600 |
| 19 | 44750700849254400 |
| 20 | 895014687427660800 |
| 21 | 18795308435980876800 |
| 22 | 413496757432991232000 |