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 | 0 |
| 3 | 3 |
| 4 | 8 |
| 5 | 45 |
| 6 | 264 |
| 7 | 1855 |
| 8 | 14832 |
| 9 | 133497 |
| 10 | 1334960 |
| 11 | 14684571 |
| 12 | 176214856 |
| 13 | 2290793125 |
| 14 | 32071103752 |
| 15 | 481066556279 |
| 16 | 7697064900448 |
| 17 | 130850103307633 |
| 18 | 2355301859537376 |
| 19 | 44750735331210163 |
| 20 | 895014706624203240 |
| 21 | 18795308839108268061 |
| 22 | 413496794460381897320 |