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 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 17 |
| 7 | 49 |
| 8 | 156 |
| 9 | 520 |
| 10 | 1762 |
| 11 | 6110 |
| 12 | 21713 |
| 13 | 78469 |
| 14 | 287393 |
| 15 | 1065951 |
| 16 | 3998286 |
| 17 | 15140500 |
| 18 | 57817817 |
| 19 | 222478829 |
| 20 | 861952579 |
| 21 | 3360043843 |
| 22 | 13171307962 |