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 | -5 |
| 4 | 25 |
| 5 | -131 |
| 6 | 793 |
| 7 | -6137 |
| 8 | 60049 |
| 9 | -670919 |
| 10 | 7930321 |
| 11 | -96775853 |
| 12 | 1225237609 |
| 13 | -16333089227 |
| 14 | 232150489129 |
| 15 | -3531321746465 |
| 16 | 57178717416097 |
| 17 | -975918663642767 |
| 18 | 17400776511175201 |
| 19 | -322309002081819221 |
| 20 | 6188520430773389881 |
| 21 | -123166171374344928275 |
| 22 | 2542231599282355411897 |