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 | 1 |
| 2 | -3 |
| 3 | 9 |
| 4 | -37 |
| 5 | 171 |
| 6 | -849 |
| 7 | 4421 |
| 8 | -23820 |
| 9 | 131676 |
| 10 | -742616 |
| 11 | 4255944 |
| 12 | -24714276 |
| 13 | 145103426 |
| 14 | -859920585 |
| 15 | 5137093695 |
| 16 | -30902681230 |
| 17 | 187034086170 |
| 18 | -1138106903928 |
| 19 | 6958662440416 |
| 20 | -42729903714420 |
| 21 | 263400623938140 |
| 22 | -1629378251621535 |
| 23 | 10111374706286895 |