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) |
|---|---|
| 2 | 0 |
| 3 | 0 |
| 4 | 4 |
| 5 | 704 |
| 6 | 553008 |
| 7 | 13802629632 |
| 8 | 1782158930138112 |
| 9 | 14231924675064000331776 |