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 | 2 |
| 2 | 120 |
| 3 | 20880 |
| 4 | 7244160 |
| 5 | 4193683200 |
| 6 | 3648171985920 |
| 7 | 4450790792448000 |
| 8 | 7251098441261875200 |
| 9 | 15208619045076276019200 |
| 10 | 39919072914444753469440000 |
| 11 | 128188338317208930555828633600 |
| 12 | 494389344738688341547326898176000 |
| 13 | 2255096937522349816552823932846080000 |