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 | 2 |
| 4 | 24 |
| 5 | 300 |
| 6 | 4480 |
| 7 | 78750 |
| 8 | 1591296 |
| 9 | 36355256 |
| 10 | 927244800 |
| 11 | 26127386010 |
| 12 | 806251494400 |
| 13 | 27046291980708 |
| 14 | 980094896062464 |
| 15 | 38158333538165750 |
| 16 | 1588601646620835840 |
| 17 | 70427042234715548400 |
| 18 | 3312574102411273437184 |
| 19 | 164767312911755127462066 |
| 20 | 8641342923227371929600000 |