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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 0 |
| 6 | 0 |
| 7 | 16 |
| 8 | -18 |
| 9 | 0 |
| 10 | 252 |
| 11 | -576 |
| 12 | 519 |
| 13 | 3264 |
| 14 | -12468 |
| 15 | 20568 |
| 16 | 26662 |
| 17 | -215568 |
| 18 | 528576 |
| 19 | -164616 |
| 20 | -3014889 |
| 21 | 10894920 |
| 22 | -13796840 |
| 23 | -29909616 |
| 24 | 190423962 |
| 25 | -399739840 |
| 26 | -22768752 |
| 27 | 2803402560 |
| 28 | -8743064909 |