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 | 6 |
| 3 | 5 |
| 4 | 140 |
| 5 | 1260 |
| 6 | 110 |
| 7 | 60060 |
| 8 | 72072 |
| 9 | 680680 |
| 10 | 12932920 |
| 11 | 38798760 |
| 12 | 11440660 |
| 13 | 185910725 |
| 14 | 5736673800 |
| 15 | 4621209450 |
| 16 | 3438179830800 |
| 17 | 10314539492400 |
| 18 | 140744203600 |
| 19 | 59365905078480 |
| 20 | 127212653739600 |
| 21 | 4056670180362800 |