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 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 70 |
| 6 | 330 |
| 7 | 1694 |
| 8 | 9202 |
| 9 | 53334 |
| 10 | 332090 |
| 11 | 2212782 |
| 12 | 15638370 |
| 13 | 116365990 |
| 14 | 907975146 |
| 15 | 7413080510 |
| 16 | 63212284498 |
| 17 | 561747543414 |
| 18 | 5190343710746 |
| 19 | 49752410984526 |
| 20 | 493844719701186 |
| 21 | 5068209425457862 |
| 22 | 53705511911500746 |
| 23 | 586862875255860062 |
| 24 | 6605213319604075186 |