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 | 1 |
| 4 | -6 |
| 5 | 46 |
| 6 | -440 |
| 7 | 5076 |
| 8 | -68740 |
| 9 | 1070056 |
| 10 | -18835164 |
| 11 | 369994780 |
| 12 | -8025080096 |
| 13 | 190501729848 |
| 14 | -4912802070280 |
| 15 | 136775150153656 |
| 16 | -4088669684755440 |
| 17 | 130620500241909376 |
| 18 | -4441243727496127184 |
| 19 | 160132524268963159440 |
| 20 | -6102784264210449418144 |