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 | 1 |
| 2 | 4 |
| 3 | 18 |
| 4 | 80 |
| 5 | 365 |
| 6 | 1692 |
| 7 | 7945 |
| 8 | 37648 |
| 9 | 179595 |
| 10 | 861020 |
| 11 | 4143832 |
| 12 | 20004096 |
| 13 | 96810779 |
| 14 | 469508340 |
| 15 | 2281123530 |
| 16 | 11100465216 |
| 17 | 54093131147 |
| 18 | 263929559436 |
| 19 | 1289217255934 |
| 20 | 6303934406640 |
| 21 | 30853639964847 |
| 22 | 151139139048084 |