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 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | -7 |
| 5 | -15 |
| 6 | 25 |
| 7 | 287 |
| 8 | 721 |
| 9 | -2847 |
| 10 | -30255 |
| 11 | -61697 |
| 12 | 682761 |
| 13 | 5861713 |
| 14 | 3105193 |
| 15 | -258188513 |
| 16 | -1681060063 |
| 17 | 4623681473 |
| 18 | 135471132705 |
| 19 | 564325398271 |
| 20 | -6357495670375 |
| 21 | -89817656595791 |
| 22 | -84337394884167 |
| 23 | 7820620314702879 |
| 24 | 67277670159083761 |
| 25 | -322108989883888479 |