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 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 24 |
| 6 | 120 |
| 7 | 720 |
| 8 | 5040 |
| 9 | 40320 |
| 10 | 181440 |
| 11 | 1209600 |
| 12 | 9979200 |
| 13 | 95800320 |
| 14 | 1037836800 |
| 15 | 12454041600 |
| 16 | 163459296000 |
| 17 | 2324754432000 |
| 18 | 19760412672000 |
| 19 | 237124952064000 |
| 20 | 3379030566912000 |
| 21 | 54064489070592000 |
| 22 | 946128558735360000 |
| 23 | 17841281393295360000 |