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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 20 |
| 5 | 115 |
| 6 | 715 |
| 7 | 4683 |
| 8 | 31824 |
| 9 | 222300 |
| 10 | 1586310 |
| 11 | 11514030 |
| 12 | 84742320 |
| 13 | 630946446 |
| 14 | 4743789260 |
| 15 | 35965715780 |
| 16 | 274659794160 |
| 17 | 2110810059795 |
| 18 | 16312695488265 |
| 19 | 126693445737170 |
| 20 | 988340783454380 |
| 21 | 7740875273884445 |
| 22 | 60846920004855985 |
| 23 | 479854293574853085 |