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 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 30 |
| 6 | 117 |
| 7 | 512 |
| 8 | 2597 |
| 9 | 14892 |
| 10 | 99034 |
| 11 | 721350 |
| 12 | 5909324 |
| 13 | 52578654 |
| 14 | 516148082 |
| 15 | 5422071091 |
| 16 | 61889692290 |
| 17 | 749456672155 |
| 18 | 9767058240577 |
| 19 | 134007989313530 |
| 20 | 1958535749524107 |