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 | 0 |
| 3 | -15 |
| 4 | -112 |
| 5 | -135 |
| 6 | 9504 |
| 7 | 152425 |
| 8 | 610560 |
| 9 | -27692847 |
| 10 | -765107200 |
| 11 | -6289891839 |
| 12 | 213472972800 |
| 13 | 9380264146825 |
| 14 | 129378550468608 |
| 15 | -3294028613874375 |
| 16 | -226623617585053696 |
| 17 | -4707649131227927775 |
| 18 | 83803818828756418560 |
| 19 | 9446689798312021406353 |
| 20 | 277055229100887244800000 |