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 | 0 |
| 4 | 24 |
| 5 | 120 |
| 6 | 660 |
| 7 | 4200 |
| 8 | 30688 |
| 9 | 254016 |
| 10 | 2352240 |
| 11 | 24108480 |
| 12 | 271016064 |
| 13 | 3316135680 |
| 14 | 43877957760 |
| 15 | 624306009600 |
| 16 | 9505324339200 |
| 17 | 154205312163840 |
| 18 | 2655567756979200 |
| 19 | 48382249157222400 |
| 20 | 929788248840192000 |
| 21 | 18796669969158144000 |
| 22 | 398766195659497881600 |