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 | 2 |
| 3 | 6 |
| 4 | 48 |
| 5 | 760 |
| 6 | 21840 |
| 7 | 1121568 |
| 8 | 104510336 |
| 9 | 18111498624 |
| 10 | 5966666196480 |
| 11 | 3794613745429760 |
| 12 | 4704698796461841408 |
| 13 | 11443317008255593064448 |
| 14 | 54831540882238864189229056 |
| 15 | 519046250316393184411087165440 |
| 16 | 9726643425055315256306341282775040 |