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 | 1 |
| 4 | -19 |
| 5 | 9 |
| 6 | -863 |
| 7 | 1375 |
| 8 | -33953 |
| 9 | 57281 |
| 10 | -3250433 |
| 11 | 1891755 |
| 12 | -13695779093 |
| 13 | 24466579093 |
| 14 | -132282840127 |
| 15 | 240208245823 |
| 16 | -111956703448001 |
| 17 | 4573423873125 |
| 18 | -30342376302478019 |
| 19 | 56310194579604163 |