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 | 1 |
| 3 | -1 |
| 4 | 4 |
| 5 | -24 |
| 6 | 2304 |
| 7 | 368640 |
| 8 | 6210846720 |
| 9 | 2086844497920 |
| 10 | 27369126116720640000 |