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 | 3 |
| 2 | 16 |
| 3 | 90 |
| 4 | 576 |
| 5 | 4200 |
| 6 | 34560 |
| 7 | 317520 |
| 8 | 3225600 |
| 9 | 35925120 |
| 10 | 435456000 |
| 11 | 5708102400 |
| 12 | 80472268800 |
| 13 | 1214269056000 |
| 14 | 19527937228800 |
| 15 | 333456963840000 |
| 16 | 6025763487744000 |
| 17 | 114887039275008000 |
| 18 | 2304854534062080000 |