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 | 1 |
| 3 | 8 |
| 4 | -8 |
| 5 | 224 |
| 6 | -712 |
| 7 | 9120 |
| 8 | -53496 |
| 9 | 980088 |
| 10 | -14394648 |
| 11 | 264140832 |
| 12 | -4113747024 |
| 13 | 59028225840 |
| 14 | -545558201424 |
| 15 | -4191307074432 |
| 16 | 450100910950272 |
| 17 | -17302659472138752 |
| 18 | 530508727766191104 |
| 19 | -14790496500550616832 |
| 20 | 408513443917280375808 |
| 21 | -12274212131738107257600 |