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 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 17 |
| 5 | 121 |
| 6 | 891 |
| 7 | 7155 |
| 8 | 63351 |
| 9 | 617463 |
| 10 | 6590727 |
| 11 | 76589127 |
| 12 | 963486567 |
| 13 | 13052781927 |
| 14 | 189537379047 |
| 15 | 2937560365287 |
| 16 | 48409889869287 |
| 17 | 845393769958887 |
| 18 | 15596602532173287 |
| 19 | 303139660882458087 |
| 20 | 6191620542649779687 |