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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 120 |
| 6 | 600 |
| 7 | 3720 |
| 8 | 27240 |
| 9 | 229080 |
| 10 | 2170680 |
| 11 | 22852200 |
| 12 | 264398280 |
| 13 | 3332744760 |
| 14 | 45440868120 |
| 15 | 666166856520 |
| 16 | 10446911529000 |
| 17 | 174478419885720 |
| 18 | 3091496076405240 |
| 19 | 57915148833808680 |
| 20 | 1143668772912038280 |
| 21 | 23742102690747895800 |
| 22 | 516882856872298424280 |
| 23 | 11775038596933279562760 |