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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 156 |
| 6 | 4800 |
| 7 | 208440 |
| 8 | 11939760 |
| 9 | 874681920 |
| 10 | 79795860480 |
| 11 | 8873760470400 |
| 12 | 1181869427692800 |
| 13 | 185755937440550400 |
| 14 | 34022680848982425600 |
| 15 | 7183771725162237004800 |
| 16 | 1732270657442505852672000 |
| 17 | 473131604733608510097408000 |
| 18 | 145308345869661566419795968000 |