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 | 3 |
| 2 | 15 |
| 3 | 85 |
| 4 | 531 |
| 5 | 3545 |
| 6 | 24833 |
| 7 | 180251 |
| 8 | 1344163 |
| 9 | 10237001 |
| 10 | 79287469 |
| 11 | 622596063 |
| 12 | 4945078477 |
| 13 | 39658283943 |
| 14 | 320689293119 |
| 15 | 2611817435525 |
| 16 | 21405148148051 |
| 17 | 176396318594937 |
| 18 | 1460795339822349 |
| 19 | 12150467810552223 |
| 20 | 101463416752305385 |
| 21 | 850306144532133787 |