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 | 6 |
| 4 | 36 |
| 5 | 240 |
| 6 | 1800 |
| 7 | 16800 |
| 8 | 191520 |
| 9 | 2328480 |
| 10 | 30240000 |
| 11 | 479001600 |
| 12 | 8083152000 |
| 13 | 142702560000 |
| 14 | 2731586457600 |
| 15 | 59056027430400 |
| 16 | 1320663933388800 |
| 17 | 30575780537702400 |
| 18 | 783699448602470400 |
| 19 | 21234672840116736000 |
| 20 | 591499300737945600000 |