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 | -9 |
| 2 | 227 |
| 3 | -585 |
| 4 | 61327 |
| 5 | -25545 |
| 6 | 3058997 |
| 7 | -836745 |
| 8 | 80906767 |
| 9 | -32625801 |
| 10 | 3260040385 |
| 11 | -55137225 |
| 12 | 23182815610837 |
| 13 | -228884877897 |
| 14 | -10473784700701 |
| 15 | 68553926774775 |
| 16 | 360941520655007999 |
| 17 | -30573539999341833 |
| 18 | -279346287039955579921 |
| 19 | 16938924643713296055 |