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 | -3 |
| 3 | -17 |
| 4 | 49 |
| 5 | 651 |
| 6 | -1259 |
| 7 | -38023 |
| 8 | 26433 |
| 9 | 2969299 |
| 10 | 2225101 |
| 11 | -289389891 |
| 12 | -692529551 |
| 13 | 33718183045 |
| 14 | 143578976997 |
| 15 | -4559187616649 |
| 16 | -29119975483135 |
| 17 | 699788001188403 |
| 18 | 6188699469443869 |
| 19 | -119828491083854707 |
| 20 | -1404529670244379599 |
| 21 | 22563726025297759345 |
| 22 | 341997845736800473397 |