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 | -3 |
| 4 | 16 |
| 5 | 90 |
| 6 | -204 |
| 7 | -4200 |
| 8 | -5312 |
| 9 | 254016 |
| 10 | 1586160 |
| 11 | -17970480 |
| 12 | -294932736 |
| 13 | 790115040 |
| 14 | 54224747136 |
| 15 | 216483714720 |
| 16 | -10481294822400 |
| 17 | -137535688281600 |
| 18 | 1798183916660736 |
| 19 | 58769251106526720 |
| 20 | -95282580797291520 |
| 21 | -23811620975395061760 |
| 22 | -203282679617698222080 |