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 | 6 |
| 5 | 205 |
| 6 | 5700 |
| 7 | 156555 |
| 8 | 4483360 |
| 9 | 136368414 |
| 10 | 4432075200 |
| 11 | 154060613850 |
| 12 | 5720327205120 |
| 13 | 226378594906035 |
| 14 | 9523895202838016 |
| 15 | 424814409531910125 |
| 16 | 20037831121798963200 |
| 17 | 996964614369038858060 |
| 18 | 52198565072252054814720 |
| 19 | 2869621989939313379211204 |
| 20 | 165302832533722012508160000 |