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) |
|---|---|
| 4 | 1 |
| 5 | 60 |
| 6 | 207360 |
| 7 | 2407897497600 |
| 8 | 318060088262309047173120000 |
| 9 | 5462759866253102351440025387291465047015528857600000000 |