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) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 30 |
| 5 | 605 |
| 6 | 9030 |
| 7 | 110901 |
| 8 | 1200150 |
| 9 | 11932285 |
| 10 | 111885510 |
| 11 | 1006471301 |
| 12 | 8786447670 |
| 13 | 75039565965 |
| 14 | 630534185190 |
| 15 | 5234341175701 |
| 16 | 43059373189590 |
| 17 | 351805681631645 |
| 18 | 2859550165976070 |
| 19 | 23152657123816101 |
| 20 | 186907026783617910 |
| 21 | 1505512392025329325 |