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 | 0 |
| 4 | 1 |
| 5 | 4 |
| 6 | 28 |
| 7 | 85 |
| 8 | 630 |
| 9 | 3096 |
| 10 | 23220 |
| 11 | 123952 |
| 12 | 1036080 |
| 13 | 7230828 |
| 14 | 66349440 |
| 15 | 500721252 |
| 16 | 5080269600 |
| 17 | 45925520096 |
| 18 | 508031496000 |
| 19 | 4919774752448 |
| 20 | 59256847036800 |
| 21 | 656763354386032 |
| 22 | 8532986691801600 |
| 23 | 100525956801641104 |
| 24 | 1405335512577427200 |
| 25 | 18431883446961030912 |