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 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 48 |
| 5 | 432 |
| 6 | 5184 |
| 7 | 82944 |
| 8 | 1658880 |
| 9 | 41472000 |
| 10 | 1244160000 |
| 11 | 44789760000 |
| 12 | 1881169920000 |
| 13 | 92177326080000 |
| 14 | 5161930260480000 |
| 15 | 330363536670720000 |
| 16 | 23786174640291840000 |
| 17 | 1926680145863639040000 |
| 18 | 173401213127727513600000 |
| 19 | 17340121312772751360000000 |