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 | 4320 |
| 8 | 34560 |
| 9 | 311040 |
| 10 | 3110400 |
| 11 | 34214400 |
| 12 | 410572800 |
| 13 | 5337446400 |
| 14 | 69386803200 |
| 15 | 1040802048000 |
| 16 | 16652832768000 |
| 17 | 283098157056000 |
| 18 | 5095766827008000 |
| 19 | 96819569713152000 |
| 20 | 1936391394263040000 |
| 21 | 38727827885260800000 |
| 22 | 852012213475737600000 |