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 | 1 |
| 2 | 0 |
| 3 | 6 |
| 4 | 24 |
| 5 | 480 |
| 6 | 5760 |
| 7 | 126000 |
| 8 | 2580480 |
| 9 | 69310080 |
| 10 | 1959552000 |
| 11 | 64505548800 |
| 12 | 2292022656000 |
| 13 | 90366525849600 |
| 14 | 3843167789260800 |
| 15 | 177248722210560000 |
| 16 | 8758468152225792000 |
| 17 | 463225965106544640000 |
| 18 | 26058454876652470272000 |