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 | -1 |
| 2 | 0 |
| 3 | -6 |
| 4 | -8 |
| 5 | -120 |
| 6 | -96 |
| 7 | -5040 |
| 8 | -4320 |
| 9 | -362880 |