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 | 3 |
| 4 | 21 |
| 5 | 273 |
| 6 | 5737 |
| 7 | 177919 |
| 8 | 7651849 |
| 9 | 436186313 |
| 10 | 31842549569 |
| 11 | 2897710853939 |
| 12 | 321648004495773 |
| 13 | 42779331295225353 |
| 14 | 6716367934603667145 |
| 15 | 1229096733282700520799 |
| 16 | 259339594018913458094865 |
| 17 | 62500870590534491566841265 |
| 18 | 17062742827503910747790541249 |
| 19 | 5238263128497776755775631825219 |