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 | 0 |
| 2 | -1 |
| 3 | -2 |
| 4 | -4 |
| 5 | 0 |
| 6 | 44 |
| 7 | 288 |
| 8 | 1276 |
| 9 | 0 |
| 10 | -96976 |
| 11 | -1707552 |
| 12 | -19298224 |
| 13 | 0 |
| 14 | 10054374704 |
| 15 | 465280599168 |
| 16 | 13714167096256 |
| 17 | 0 |
| 18 | -48973290700730176 |
| 19 | -5936600776414758912 |
| 20 | -457851294761126415424 |
| 21 | 0 |
| 22 | 11206368290573330143917824 |
| 23 | 3556757207429750327041640448 |