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 | 0 |
| 3 | 2 |
| 4 | -8 |
| 5 | 64 |
| 6 | -304 |
| 7 | 3968 |
| 8 | -43392 |
| 9 | 378880 |
| 10 | -4002816 |
| 11 | 68247552 |
| 12 | -995736576 |
| 13 | 15949529088 |
| 14 | -238273241088 |
| 15 | 4760383438848 |
| 16 | -113132156780544 |
| 17 | 2119956936523776 |
| 18 | -42743492966350848 |
| 19 | 1123874181449515008 |
| 20 | -28901050300546154496 |
| 21 | 722523072906903158784 |
| 22 | -19401957422023594475520 |
| 23 | 589068777481530305937408 |