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 | 2 |
| 3 | 6 |
| 4 | 25 |
| 5 | 125 |
| 6 | 750 |
| 7 | 5251 |
| 8 | 42008 |
| 9 | 378072 |
| 10 | 3780721 |
| 11 | 41587931 |
| 12 | 499055172 |
| 13 | 6487717237 |
| 14 | 90828041318 |
| 15 | 1362420619770 |
| 16 | 21798729916321 |
| 17 | 370578408577457 |
| 18 | 6670411354394226 |
| 19 | 126737815733490295 |
| 20 | 2534756314669805900 |
| 21 | 53229882608065923900 |
| 22 | 1171057417377450325801 |