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 | 1 |
| 3 | 0 |
| 4 | -2 |
| 5 | 4 |
| 6 | 0 |
| 7 | -24 |
| 8 | 68 |
| 9 | 20 |
| 10 | -936 |
| 11 | 3800 |
| 12 | -2172 |
| 13 | -64120 |
| 14 | 417752 |
| 15 | -959852 |
| 16 | -5464092 |
| 17 | 68816400 |
| 18 | -328509112 |
| 19 | 8361828 |
| 20 | 13473157664 |
| 21 | -119068537700 |
| 22 | 448312242012 |
| 23 | 1868795480588 |
| 24 | -43889516937276 |
| 25 | 348963546501928 |
| 26 | -1006637409183472 |
| 27 | -12316833304447344 |
| 28 | 217304253286437480 |