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 | -2 |
| 3 | 20 |
| 4 | -504 |
| 5 | 25200 |
| 6 | -2189088 |
| 7 | 302702400 |
| 8 | -62564261760 |
| 9 | 18427508985600 |
| 10 | -7449695786856960 |
| 11 | 4010313259477324800 |
| 12 | -2803674333549374208000 |
| 13 | 2492728196309155284480000 |
| 14 | -2768630339381333070099456000 |