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 | 2 |
| 2 | 8 |
| 3 | 44 |
| 4 | 296 |
| 5 | 2312 |
| 6 | 20384 |
| 7 | 199376 |
| 8 | 2138336 |
| 9 | 24936416 |
| 10 | 314142848 |
| 11 | 4252773824 |
| 12 | 61594847360 |
| 13 | 950757812864 |
| 14 | 15586971531776 |
| 15 | 270569513970944 |
| 16 | 4959071121374720 |
| 17 | 95721139472072192 |
| 18 | 1941212789888952320 |
| 19 | 41271304403571227648 |
| 20 | 918030912312297752576 |
| 21 | 21325054720042613565440 |