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 | 12 |
| 4 | 165 |
| 5 | 1430 |
| 6 | 10010 |
| 7 | 61880 |
| 8 | 352716 |
| 9 | 1899240 |
| 10 | 9806280 |
| 11 | 49031400 |
| 12 | 239028075 |
| 13 | 1141710570 |
| 14 | 5362579950 |
| 15 | 24837212400 |
| 16 | 113678010600 |
| 17 | 515030986800 |
| 18 | 2312957340720 |
| 19 | 10307744670600 |
| 20 | 45626928615450 |
| 21 | 200758485907980 |
| 22 | 878623171119540 |
| 23 | 3826892034209552 |
| 24 | 16596215454480200 |
| 25 | 71691488703052400 |
| 26 | 308585103547921200 |
| 27 | 1323929637802371600 |