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 | -2 |
| 4 | 7 |
| 5 | 3 |
| 6 | -242 |
| 7 | 2032 |
| 8 | -3795 |
| 9 | -187211 |
| 10 | 3860140 |
| 11 | -36467310 |
| 12 | -284357501 |
| 13 | 21796446487 |
| 14 | -538332144294 |
| 15 | 5605176351652 |
| 16 | 182065102478857 |
| 17 | -12963817679287959 |
| 18 | 422751776737348504 |
| 19 | -5483284328996107802 |
| 20 | -327213964461103956801 |
| 21 | 30082452646697648945899 |