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 | 4320 |
| 7 | 52920 |
| 8 | 376320 |
| 9 | 1905120 |
| 10 | 7620480 |
| 11 | 25613280 |
| 12 | 75271680 |
| 13 | 198764280 |
| 14 | 480960480 |
| 15 | 1082161080 |
| 16 | 2289530880 |
| 17 | 4594961280 |
| 18 | 8809274880 |
| 19 | 16225246080 |
| 20 | 28844881920 |
| 21 | 49689816120 |
| 22 | 83217546720 |
| 23 | 135870624120 |