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 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 36 |
| 4 | 228 |
| 5 | 1518 |
| 6 | 10530 |
| 7 | 75516 |
| 8 | 556512 |
| 9 | 4194801 |
| 10 | 32224114 |
| 11 | 251565996 |
| 12 | 1991331720 |
| 13 | 15953808780 |
| 14 | 129171585690 |
| 15 | 1055640440268 |
| 16 | 8698890336576 |
| 17 | 72215877581844 |
| 18 | 603532770013080 |
| 19 | 5074488683389840 |