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) |
|---|---|
| 1 | 2 |
| 2 | 2 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 720 |
| 7 | 10080 |
| 8 | 241920 |
| 9 | 5080320 |
| 10 | 108864000 |
| 11 | 2474841600 |
| 12 | 60833203200 |
| 13 | 1569209241600 |
| 14 | 42978897561600 |
| 15 | 1265828788224000 |
| 16 | 38916389191680000 |
| 17 | 1280474741145600000 |
| 18 | 44189183316934656000 |