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 | -17 |
| 3 | -53 |
| 4 | 865 |
| 5 | 4681 |
| 6 | -73169 |
| 7 | -578717 |
| 8 | 8640577 |
| 9 | 91975825 |
| 10 | -1307797649 |
| 11 | -17863446149 |
| 12 | 241080488353 |
| 13 | 4099584856537 |
| 14 | -52313249418065 |
| 15 | -1085408633265389 |
| 16 | 13039168709612161 |
| 17 | 325636855090044193 |
| 18 | -3664348770051277073 |
| 19 | -109170689819225595605 |
| 20 | 1144036589538311163361 |