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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | -6 |
| 7 | 21 |
| 8 | -56 |
| 9 | 126 |
| 10 | -126 |
| 11 | -2310 |
| 12 | 32472 |
| 13 | -287001 |
| 14 | 2016014 |
| 15 | -11978967 |
| 16 | 58518096 |
| 17 | -159272932 |
| 18 | -1367358552 |
| 19 | 33638536548 |
| 20 | -450849366456 |
| 21 | 4857267575853 |
| 22 | -44901867052350 |
| 23 | 349150315551037 |
| 24 | -1912043403523176 |
| 25 | -2260563011376054 |