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 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 20 |
| 7 | 0 |
| 8 | 1121 |
| 9 | 72828 |
| 10 | 872640 |
| 11 | 9037710 |
| 12 | 118590450 |
| 13 | 1743739426 |
| 14 | 24407782672 |
| 15 | 424735169040 |
| 16 | 7802802463460 |
| 17 | 135385454550288 |
| 18 | 2823521345232834 |
| 19 | 59332856029292241 |
| 20 | 1238888844244575904 |
| 21 | 28893281420537822022 |
| 22 | 684650546073054870188 |
| 23 | 16342742577592266281996 |