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 | -4 |
| 3 | -3 |
| 4 | 132 |
| 5 | -375 |
| 6 | -8298 |
| 7 | 86121 |
| 8 | 636696 |
| 9 | -20318607 |
| 10 | 15154290 |
| 11 | 5555366289 |
| 12 | -57903946092 |
| 13 | -1608939709767 |
| 14 | 44662076643870 |
| 15 | 329040381072825 |
| 16 | -31446740971136592 |
| 17 | 195779189199531105 |
| 18 | 21694625692807192938 |
| 19 | -496937940680594097279 |