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 | 1 |
| 5 | 1 |
| 6 | -1 |
| 7 | -17 |
| 8 | 17 |
| 9 | 31 |
| 10 | -31 |
| 11 | -691 |
| 12 | 691 |
| 13 | 5461 |
| 14 | -5461 |
| 15 | -929569 |
| 16 | 929569 |
| 17 | 3202291 |
| 18 | -3202291 |
| 19 | -221930581 |
| 20 | 221930581 |
| 21 | 4722116521 |
| 22 | -4722116521 |
| 23 | -968383680827 |
| 24 | 968383680827 |
| 25 | 14717667114151 |
| 26 | -14717667114151 |