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 | 2 |
| 3 | -6 |
| 4 | 22 |
| 5 | -90 |
| 6 | 394 |
| 7 | -1806 |
| 8 | 8558 |
| 9 | -41586 |
| 10 | 206098 |
| 11 | -1037718 |
| 12 | 5293446 |
| 13 | -27297738 |
| 14 | 142078746 |
| 15 | -745387038 |
| 16 | 3937603038 |
| 17 | -20927156706 |
| 18 | 111818026018 |
| 19 | -600318853926 |
| 20 | 3236724317174 |
| 21 | -17518619320890 |
| 22 | 95149655201962 |
| 23 | -518431875418926 |
| 24 | 2832923350929742 |
| 25 | -15521467648875090 |