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) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 24 |
| 5 | 184 |
| 6 | 1911 |
| 7 | 24252 |
| 8 | 362199 |
| 9 | 6162080 |
| 10 | 117342912 |
| 11 | 2469791336 |
| 12 | 56919388745 |
| 13 | 1425435420600 |
| 14 | 38543562608825 |
| 15 | 1119188034056244 |
| 16 | 34733368101580440 |
| 17 | 1147320305439301344 |
| 18 | 40190943859500501151 |
| 19 | 1488212241729974297796 |
| 20 | 58080468361734193793551 |