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 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 132 |
| 5 | 792 |
| 6 | 33264 |
| 7 | 266112 |
| 8 | 19958400 |
| 9 | 618710400 |
| 10 | 66820723200 |
| 11 | 801848678400 |
| 12 | 1425686950195200 |
| 13 | 19959617302732800 |
| 14 | 4111681164362956800 |
| 15 | 962133392460931891200 |
| 16 | 1057384598314564148428800 |
| 17 | 19032922769662154671718400 |
| 18 | 112313277263776374717810278400 |