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 | 0 |
| 4 | 1 |
| 5 | 3 |
| 6 | 9 |
| 7 | 48 |
| 8 | 306 |
| 9 | 2190 |
| 10 | 17810 |
| 11 | 162480 |
| 12 | 1642635 |
| 13 | 18231465 |
| 14 | 220420179 |
| 15 | 2883693792 |
| 16 | 40592133316 |
| 17 | 611765693532 |
| 18 | 9828843229764 |
| 19 | 167702100599520 |
| 20 | 3028466654021205 |
| 21 | 57708568527002415 |
| 22 | 1157199837194069405 |
| 23 | 24358905149602459920 |
| 24 | 537053113128448187766 |