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 | 14 |
| 4 | 48 |
| 5 | 416 |
| 6 | 3360 |
| 7 | 29504 |
| 8 | 274176 |
| 9 | 3503104 |
| 10 | 45192960 |
| 11 | 579956992 |
| 12 | 8982251520 |
| 13 | 138130720768 |
| 14 | 2456648183808 |
| 15 | 45868468109312 |
| 16 | 871166211686400 |
| 17 | 17536583860060160 |
| 18 | 393972064172900352 |
| 19 | 8704569607311982592 |
| 20 | 210657904645299240960 |
| 21 | 5322004254737369399296 |