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 | -1 |
| 3 | -11 |
| 4 | -11 |
| 5 | 381 |
| 6 | 2461 |
| 7 | -21083 |
| 8 | -449623 |
| 9 | 221113 |
| 10 | 99327961 |
| 11 | 862237641 |
| 12 | -24117649907 |
| 13 | -612442461227 |
| 14 | 3958786971413 |
| 15 | 388794711373741 |
| 16 | 2915530533136081 |
| 17 | -239559177608638095 |
| 18 | -6208842113295032015 |
| 19 | 118603625804273873809 |
| 20 | 8571701737898867135861 |