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 | 0 |
| 2 | 1 |
| 3 | -7 |
| 4 | 81 |
| 5 | -1181 |
| 6 | 21373 |
| 7 | -462267 |
| 8 | 11663137 |
| 9 | -336711385 |
| 10 | 10955316501 |
| 11 | -396815693759 |
| 12 | 15840688752529 |
| 13 | -691086583866069 |
| 14 | 32717602050027469 |
| 15 | -1670649590632148611 |
| 16 | 91530694441643402817 |
| 17 | -5355984871255569700913 |
| 18 | 333392838283336197688741 |