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) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | -4 |
| 4 | -8 |
| 5 | 32 |
| 6 | 216 |
| 7 | -264 |
| 8 | -7552 |
| 9 | -9216 |
| 10 | 349568 |
| 11 | 1548032 |
| 12 | -20281216 |
| 13 | -190744448 |
| 14 | 1350879232 |
| 15 | 25395878400 |
| 16 | -84211707904 |
| 17 | -3862395551744 |
| 18 | -286327484416 |
| 19 | 674521189158912 |
| 20 | 2529465981566976 |
| 21 | -133945803441307648 |