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 | 0 |
| 3 | 3 |
| 4 | -24 |
| 5 | 175 |
| 6 | -1314 |
| 7 | 10339 |
| 8 | -84448 |
| 9 | 696429 |
| 10 | -5444700 |
| 11 | 32897601 |
| 12 | 53444304 |
| 13 | -8071238721 |
| 14 | 235927045536 |
| 15 | -5630771421765 |
| 16 | 126525509087232 |
| 17 | -2799633511755963 |
| 18 | 62154971516786616 |
| 19 | -1396560425289392007 |
| 20 | 31880150704745078400 |
| 21 | -740188445913015688953 |