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 | 1 |
| 3 | 3 |
| 4 | 11 |
| 5 | 48 |
| 6 | 248 |
| 7 | 1500 |
| 8 | 10476 |
| 9 | 83328 |
| 10 | 745344 |
| 11 | 7413120 |
| 12 | 81187200 |
| 13 | 970928640 |
| 14 | 12589240320 |
| 15 | 175900757760 |
| 16 | 2634526944000 |
| 17 | 42103369728000 |
| 18 | 715107004416000 |
| 19 | 12862666543104000 |
| 20 | 244249409359872000 |
| 21 | 4882687056543744000 |
| 22 | 102496533840691200000 |