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 | 4 |
| 2 | 16 |
| 3 | 84 |
| 4 | 576 |
| 5 | 5820 |
| 6 | 72720 |
| 7 | 1181460 |
| 8 | 21984480 |
| 9 | 493882620 |
| 10 | 13996733520 |
| 11 | 430612001820 |
| 12 | 15742074348000 |
| 13 | 641147559872820 |
| 14 | 27488197348531920 |
| 15 | 1286344285877911260 |
| 16 | 67817877972050366160 |
| 17 | 3984226025421591129180 |
| 18 | 242703493548359285922480 |
| 19 | 16211176424801583698573100 |