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 | 3 |
| 4 | 44 |
| 5 | 270 |
| 6 | 3714 |
| 7 | 44940 |
| 8 | 746528 |
| 9 | 13149864 |
| 10 | 271954440 |
| 11 | 6154715160 |
| 12 | 155055594792 |
| 13 | 4254730262640 |
| 14 | 127019898548256 |
| 15 | 4088313657038520 |
| 16 | 141301521555548160 |
| 17 | 5216698433745207360 |
| 18 | 204946906542573645504 |
| 19 | 8536144551987171202560 |