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) |
|---|---|
| 2 | 3 |
| 3 | 11 |
| 4 | 26 |
| 5 | 154 |
| 6 | 684 |
| 7 | 5508 |
| 8 | 35664 |
| 9 | 361296 |
| 10 | 3068640 |
| 11 | 37383840 |
| 12 | 392722560 |
| 13 | 5584394880 |
| 14 | 69878833920 |
| 15 | 1135360800000 |
| 16 | 16484477184000 |
| 17 | 301158902016000 |
| 18 | 4976250951168000 |
| 19 | 100951141777920000 |
| 20 | 1870345490614272000 |