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 | -1 |
| 4 | 0 |
| 5 | -1 |
| 6 | 0 |
| 7 | -1 |
| 8 | 0 |
| 9 | -2 |
| 10 | 13 |
| 11 | -141 |
| 12 | 1803 |
| 13 | -27414 |
| 14 | 487468 |
| 15 | -10026348 |
| 16 | 236192433 |
| 17 | -6317862398 |
| 18 | 190439655626 |
| 19 | -6425425249653 |
| 20 | 241207241774250 |
| 21 | -10020155328258127 |
| 22 | 458387180159766538 |
| 23 | -22989944171828251746 |
| 24 | 1259023596072554784854 |
| 25 | -75008667460769643668558 |