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 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | 1 |
| 4 | 0 |
| 5 | -2 |
| 6 | -30 |
| 7 | 446 |
| 8 | -3248 |
| 9 | 12412 |
| 10 | 16020 |
| 11 | -211356 |
| 12 | -10756944 |
| 13 | 284038272 |
| 14 | -3556910448 |
| 15 | 19122463296 |
| 16 | 135073768320 |
| 17 | -1286054192304 |
| 18 | -108801241372368 |
| 19 | 3952903127312016 |
| 20 | -65667347037774720 |
| 21 | 339816855220730784 |
| 22 | 8862271481944986336 |