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 | 1 |
| 3 | 1 |
| 4 | 6 |
| 5 | 72 |
| 6 | 720 |
| 7 | 1080 |
| 8 | 25200 |
| 9 | 40320 |
| 10 | 725760 |
| 11 | 25401600 |
| 12 | 558835200 |
| 13 | 23950080000 |
| 14 | 1120863744000 |
| 15 | 1961511552000 |
| 16 | 58845346560000 |
| 17 | 3452260331520000 |
| 18 | 4108189794508800000 |
| 19 | 7394741630115840000 |
| 20 | 521857480753889280000 |
| 21 | 948831783188889600000 |
| 22 | 39850934893933363200000 |
| 23 | 3287702128749502464000000 |