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 | 20 |
| 4 | 412 |
| 5 | 29080 |
| 6 | 7344960 |
| 7 | 6790976640 |
| 8 | 23310543674880 |
| 9 | 300020122552550400 |
| 10 | 14587151144134593024000 |
| 11 | 2695072097623041659787264000 |
| 12 | 1901191652075515716657381408768000 |
| 13 | 5141119908014521906432306538772430848000 |