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 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 60 |
| 6 | 345 |
| 7 | 2415 |
| 8 | 18480 |
| 9 | 166320 |
| 10 | 1596105 |
| 11 | 17557155 |
| 12 | 202951980 |
| 13 | 2638375740 |
| 14 | 35703612945 |
| 15 | 535554194175 |
| 16 | 8307234936000 |
| 17 | 141222993912000 |
| 18 | 2470641012464625 |
| 19 | 46942179236827875 |
| 20 | 914462992955011500 |