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) |
|---|---|
| 2 | 0 |
| 3 | 2 |
| 4 | 9 |
| 5 | 48 |
| 6 | 250 |
| 7 | 1200 |
| 8 | 5922 |
| 9 | 34160 |
| 10 | 185460 |
| 11 | 1201920 |
| 12 | 6837600 |
| 13 | 49680576 |
| 14 | 314028000 |
| 15 | 2611065600 |
| 16 | 17913619680 |
| 17 | 162456519680 |
| 18 | 1235053617600 |
| 19 | 12593800627200 |
| 20 | 99016069824000 |
| 21 | 1062491684981760 |
| 22 | 9425603347776000 |
| 23 | 114292447803494400 |
| 24 | 1026754912019865600 |