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 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 6 |
| 5 | 24 |
| 6 | 120 |
| 7 | 720 |
| 8 | 6300 |
| 9 | 58464 |
| 10 | 586656 |
| 11 | 6384960 |
| 12 | 76471560 |
| 13 | 994831200 |
| 14 | 13939507296 |
| 15 | 209097854784 |
| 16 | 3345235180560 |
| 17 | 56866395720960 |
| 18 | 1023601917024000 |
| 19 | 19448577603454464 |
| 20 | 388972171805410656 |
| 21 | 8168409582839579520 |
| 22 | 179704944537482689920 |