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 | 10 |
| 4 | 42 |
| 5 | 330 |
| 6 | 2730 |
| 7 | 39270 |
| 8 | 570570 |
| 9 | 11741730 |
| 10 | 281291010 |
| 11 | 6915878970 |
| 12 | 239378649510 |
| 13 | 8222980095330 |
| 14 | 319091739796830 |
| 15 | 14299762385778870 |
| 16 | 693386350578511590 |
| 17 | 36278497172720993190 |
| 18 | 1987938667108592728530 |
| 19 | 128824943460332246817690 |
| 20 | 8327475076517894939812170 |
| 21 | 573657473228859495079173570 |