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 | 6 |
| 2 | -48 |
| 3 | 672 |
| 4 | -10686 |
| 5 | 185472 |
| 6 | -3398304 |
| 7 | 64606080 |
| 8 | -1261584768 |
| 9 | 25141699590 |
| 10 | -509112525600 |
| 11 | 10443131883360 |
| 12 | -216500232587520 |
| 13 | 4528450460408448 |
| 14 | -95438941858567104 |
| 15 | 2024550297637849728 |
| 16 | -43190698219545864702 |
| 17 | 925997705081213764608 |
| 18 | -19940633776083900614736 |
| 19 | 431091393800371703940576 |