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 | -1 |
| 2 | 20 |
| 3 | -560 |
| 4 | 20160 |
| 5 | -887040 |
| 6 | 46126080 |
| 7 | -2767564800 |
| 8 | 188194406400 |
| 9 | -14302774886400 |
| 10 | 1201433090457600 |
| 11 | -110531844322099200 |
| 12 | 11053184432209920000 |
| 13 | -1193743918678671360000 |
| 14 | 138474294566725877760000 |
| 15 | -17170812526274008842240000 |