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 | 2 |
| 3 | -4 |
| 4 | -4 |
| 5 | 64 |
| 6 | -8 |
| 7 | -3312 |
| 8 | 14352 |
| 9 | 267776 |
| 10 | -3403744 |
| 11 | -24119360 |
| 12 | 881205184 |
| 13 | -593040384 |
| 14 | -261913919616 |
| 15 | 2567414468864 |
| 16 | 83291021050112 |
| 17 | -2080429273726976 |
| 18 | -22004502593928704 |
| 19 | 1526354137528335360 |
| 20 | -3870482611349750784 |
| 21 | -1112746657730132623360 |
| 22 | 18568218633016319670272 |