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 | 1 |
| 5 | 19 |
| 6 | 871 |
| 7 | 1091 |
| 8 | -12319 |
| 9 | -185401 |
| 10 | -1871729 |
| 11 | -16185401 |
| 12 | 124125409 |
| 13 | 2716194779 |
| 14 | 30386265911 |
| 15 | 192015557579 |
| 16 | -1519087028159 |
| 17 | -90118169425649 |
| 18 | -1286566655151329 |
| 19 | -8992926875821681 |
| 20 | 96361313388009281 |
| 21 | 5078872062174772259 |
| 22 | 107995117552995689479 |
| 23 | 996704518577739393619 |