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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 440 |
| 6 | 38368 |
| 7 | 1022320 |
| 8 | 14082528 |
| 9 | 126490352 |
| 10 | 837543200 |
| 11 | 4412818240 |
| 12 | 19447224864 |
| 13 | 74255991784 |
| 14 | 251997948736 |
| 15 | 774861621936 |
| 16 | 2191005028672 |
| 17 | 5764306674400 |
| 18 | 14243327787456 |
| 19 | 33309659739904 |
| 20 | 74194554880960 |
| 21 | 158241369977880 |
| 22 | 324605935279648 |
| 23 | 642894402918768 |