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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | -6 |
| 5 | 1 |
| 6 | 60 |
| 7 | 1 |
| 8 | -5040 |
| 9 | 20160 |
| 10 | 347760 |
| 11 | 1 |
| 12 | -59875200 |
| 13 | 1 |
| 14 | 6218372160 |
| 15 | 47221574400 |
| 16 | -1307674368000 |
| 17 | 1 |
| 18 | 177843714048000 |
| 19 | 1 |
| 20 | -126713646259200000 |
| 21 | 1219830034655232000 |
| 22 | 51090928092415411200 |
| 23 | 1 |
| 24 | -38778025108327464960000 |
| 25 | 25852016738884976640000 |