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 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 6 |
| 5 | 30 |
| 6 | 330 |
| 7 | 13530 |
| 8 | 5019630 |
| 9 | 69777876630 |
| 10 | 351229105131280530 |
| 11 | 24509789089304573335878465330 |
| 12 | 8608552999157278550998626549630446732052243030 |