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 | 0 |
| 4 | 33792 |
| 5 | 2307376 |
| 6 | 38049764 |
| 7 | 316687056 |
| 8 | 1756247962 |
| 9 | 7430841848 |
| 10 | 25895095920 |
| 11 | 77947547416 |
| 12 | 209206118486 |
| 13 | 511919916960 |
| 14 | 1160763672124 |
| 15 | 2468985096704 |
| 16 | 4973232330258 |
| 17 | 9557709330856 |
| 18 | 17631022607048 |
| 19 | 31372223986440 |
| 20 | 54066152166478 |
| 21 | 90552261553040 |