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 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 90 |
| 5 | 2040 |
| 6 | 67950 |
| 7 | 3110940 |
| 8 | 187530840 |
| 9 | 14398171200 |
| 10 | 1371785398200 |
| 11 | 158815387962000 |
| 12 | 21959547410077200 |
| 13 | 3574340599104475200 |
| 14 | 676508133623135814000 |
| 15 | 147320988741542099484000 |
| 16 | 36574751938491748341360000 |
| 17 | 10268902998771351157327104000 |