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 | -8 |
| 4 | 81 |
| 5 | 26 |
| 6 | -3815 |
| 7 | 17494 |
| 8 | 178241 |
| 9 | -2817746 |
| 10 | 3552201 |
| 11 | 315952418 |
| 12 | -3635118575 |
| 13 | -11060115936 |
| 14 | 782886068497 |
| 15 | -7772807719574 |
| 16 | -66097429593855 |
| 17 | 2841563213504406 |
| 18 | -26634464325602135 |
| 19 | -375731325639156710 |
| 20 | 14734035378180288401 |
| 21 | -142992751647059748944 |