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 | 1 |
| 3 | 2 |
| 4 | 1 |
| 5 | 18 |
| 6 | 6 |
| 7 | 360 |
| 8 | 90 |
| 9 | 12600 |
| 10 | 2520 |
| 11 | 680400 |
| 12 | 113400 |
| 13 | 52390800 |
| 14 | 7484400 |
| 15 | 5448643200 |
| 16 | 681080400 |
| 17 | 735566832000 |
| 18 | 81729648000 |
| 19 | 125046361440000 |
| 20 | 12504636144000 |
| 21 | 26134689540960000 |
| 22 | 2375880867360000 |
| 23 | 6585941764321920000 |