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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 0 |
| 4 | -5 |
| 5 | -15 |
| 6 | 46 |
| 7 | 735 |
| 8 | 2185 |
| 9 | -33390 |
| 10 | -453479 |
| 11 | -364155 |
| 12 | 57806200 |
| 13 | 681966285 |
| 14 | -3289884779 |
| 15 | -197798065920 |
| 16 | -1815938249585 |
| 17 | 33917006295885 |
| 18 | 1155429901407646 |
| 19 | 5691720408045315 |
| 20 | -408736165211351795 |
| 21 | -10271257189100959590 |
| 22 | 23948813753053818421 |
| 23 | 6626731340918542069425 |
| 24 | 124356774945741129842320 |