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 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 4990 |
| 8 | 39520 |
| 9 | 352080 |
| 10 | 3484800 |
| 11 | 37936800 |
| 12 | 450606300 |
| 13 | 5797965980 |
| 14 | 80341280840 |
| 15 | 1192794269400 |
| 16 | 18889568419200 |
| 17 | 317838157969125 |
| 18 | 5662578565559400 |
| 19 | 106488682710940108 |
| 20 | 2107992477960872320 |
| 21 | 43815112964794432080 |
| 22 | 954074378001971825930 |