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 | 5 |
| 4 | -13 |
| 5 | 207 |
| 6 | -1791 |
| 7 | 28849 |
| 8 | -438600 |
| 9 | 8619291 |
| 10 | -181134313 |
| 11 | 4381744589 |
| 12 | -115439041983 |
| 13 | 3356162869607 |
| 14 | -105668550658100 |
| 15 | 3600058076291465 |
| 16 | -131618721053773713 |
| 17 | 5146452228945999699 |
| 18 | -214171122214841864975 |
| 19 | 9454288479242533668837 |