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) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 12 |
| 5 | 60 |
| 6 | 240 |
| 7 | 720 |
| 8 | 7920 |
| 9 | 55440 |
| 10 | 1275120 |
| 11 | 16576560 |
| 12 | 480720240 |
| 13 | 19709529840 |
| 14 | 39419059680 |
| 15 | 197095298400 |
| 16 | 3350620072800 |
| 17 | 177582863858400 |
| 18 | 532748591575200 |
| 19 | 19711697888282400 |
| 20 | 59135093664847200 |