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 | 24 |
| 4 | 180 |
| 5 | 1320 |
| 6 | 9660 |
| 7 | 70896 |
| 8 | 522648 |
| 9 | 3871440 |
| 10 | 28809990 |
| 11 | 215318400 |
| 12 | 1615579680 |
| 13 | 12165491520 |
| 14 | 91905439080 |
| 15 | 696359055840 |
| 16 | 5290416835440 |
| 17 | 40291036122528 |
| 18 | 307537305284574 |
| 19 | 2352216447006480 |
| 20 | 18024996856976760 |