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 | 9 |
| 2 | 44 |
| 3 | 207 |
| 4 | 991 |
| 5 | 4752 |
| 6 | 22769 |
| 7 | 109089 |
| 8 | 522676 |
| 9 | 2504295 |
| 10 | 11998799 |
| 11 | 57489696 |
| 12 | 275449681 |
| 13 | 1319758713 |
| 14 | 6323343884 |
| 15 | 30296960703 |
| 16 | 145161459631 |
| 17 | 695510337456 |
| 18 | 3332390227649 |
| 19 | 15966440800785 |
| 20 | 76499813776276 |
| 21 | 366532628080599 |