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) |
|---|---|
| 1 | 1 |
| 2 | -2 |
| 3 | -2 |
| 4 | -8 |
| 5 | -44 |
| 6 | -296 |
| 7 | -2312 |
| 8 | -20384 |
| 9 | -199376 |
| 10 | -2138336 |
| 11 | -24936416 |
| 12 | -314142848 |
| 13 | -4252773824 |
| 14 | -61594847360 |
| 15 | -950757812864 |
| 16 | -15586971531776 |
| 17 | -270569513970944 |
| 18 | -4959071121374720 |
| 19 | -95721139472072192 |
| 20 | -1941212789888952320 |
| 21 | -41271304403571227648 |