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 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 119 |
| 6 | 694 |
| 7 | 4579 |
| 8 | 33216 |
| 9 | 259401 |
| 10 | 2147525 |
| 11 | 18632512 |
| 12 | 167969934 |
| 13 | 1563027614 |
| 14 | 14937175825 |
| 15 | 146016423713 |
| 16 | 1455402205257 |
| 17 | 14753501614541 |
| 18 | 151783381341695 |
| 19 | 1582029822426003 |
| 20 | 16681492660789425 |
| 21 | 177726496203056670 |
| 22 | 1911230701872865231 |
| 23 | 20726637978574528119 |