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 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 56 |
| 5 | 790 |
| 6 | 8380 |
| 7 | 76482 |
| 8 | 638736 |
| 9 | 5043950 |
| 10 | 38390660 |
| 11 | 285007162 |
| 12 | 2079779416 |
| 13 | 14995363110 |
| 14 | 107204473740 |
| 15 | 761823557042 |
| 16 | 5390550296096 |
| 17 | 38026057186270 |
| 18 | 267656481977620 |
| 19 | 1881017836414122 |
| 20 | 13204444871932776 |
| 21 | 92618543463601430 |
| 22 | 649270263511862300 |