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 | 64 |
| 6 | -544 |
| 7 | 3968 |
| 8 | -29952 |
| 9 | 378880 |
| 10 | -5938176 |
| 11 | 68247552 |
| 12 | -793491456 |
| 13 | 15949529088 |
| 14 | -306908848128 |
| 15 | 4760383438848 |
| 16 | -90615249567744 |
| 17 | 2119956936523776 |
| 18 | -49428158281678848 |
| 19 | 1123874181449515008 |
| 20 | -26217392043061149696 |
| 21 | 722523072906903158784 |
| 22 | -21323712124731229470720 |
| 23 | 589068777481530305937408 |