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 | 1 |
| 4 | 9 |
| 5 | -174 |
| 6 | 2575 |
| 7 | -38219 |
| 8 | 588833 |
| 9 | -9274418 |
| 10 | 141253551 |
| 11 | -1739881142 |
| 12 | -753419447 |
| 13 | 1379742127908 |
| 14 | -83720072007585 |
| 15 | 4059017293956301 |
| 16 | -184613801568558975 |
| 17 | 8254420480122200214 |
| 18 | -369177108304219471457 |
| 19 | 16608406418618863804990 |
| 20 | -750673988803431836351799 |