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 | 0 |
| 2 | 0 |
| 3 | 118 |
| 4 | 409 |
| 5 | 2368 |
| 6 | 15750 |
| 7 | 112716 |
| 8 | 845295 |
| 9 | 6551208 |
| 10 | 52035714 |
| 11 | 421286280 |
| 12 | 3463401007 |
| 13 | 28832656408 |
| 14 | 242565115858 |
| 15 | 2058945519936 |
| 16 | 17611312647075 |
| 17 | 151647023490480 |
| 18 | 1313460091978458 |
| 19 | 11435310622320552 |
| 20 | 100019000856225156 |
| 21 | 878443730199290560 |