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 | -31 |
| 2 | 434 |
| 3 | -3627 |
| 4 | 20367 |
| 5 | -84537 |
| 6 | 296825 |
| 7 | -1027805 |
| 8 | 3586700 |
| 9 | -11522204 |
| 10 | 33703882 |
| 11 | -97807604 |
| 12 | 289043659 |
| 13 | -814257997 |
| 14 | 2164448117 |
| 15 | -5763699428 |
| 16 | 15479115951 |
| 17 | -40058137473 |
| 18 | 100379076723 |
| 19 | -252617470522 |
| 20 | 633832842041 |