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) |
|---|---|
| 3 | 1 |
| 4 | 6 |
| 5 | 25 |
| 6 | 120 |
| 7 | 742 |
| 8 | 5446 |
| 9 | 45559 |
| 10 | 427275 |
| 11 | 4437279 |
| 12 | 50532669 |
| 13 | 626068404 |
| 14 | 8382651732 |
| 15 | 120614527728 |
| 16 | 1855938746160 |
| 17 | 30411098170560 |
| 18 | 528670269132480 |
| 19 | 9718179216603840 |
| 20 | 188342519176964160 |
| 21 | 3838144417230700800 |
| 22 | 82046606738914540800 |
| 23 | 1835772107381126208000 |