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 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | -6 |
| 4 | 36 |
| 5 | -20 |
| 6 | -2730 |
| 7 | 38178 |
| 8 | -93688 |
| 9 | -7711272 |
| 10 | 184968810 |
| 11 | -1036880570 |
| 12 | -66424040628 |
| 13 | 2427958996164 |
| 14 | -24081426198466 |
| 15 | -1271591203182510 |
| 16 | 66942964987695120 |
| 17 | -1027559316530335952 |
| 18 | -45046737788036457006 |
| 19 | 3332345692967904801438 |