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 | 99 |
| 4 | 689 |
| 5 | 4817 |
| 6 | 33713 |
| 7 | 235987 |
| 8 | 1651903 |
| 9 | 11563315 |
| 10 | 80943201 |
| 11 | 566602401 |
| 12 | 3966216801 |
| 13 | 27763517603 |
| 14 | 194344623215 |
| 15 | 1360412362499 |
| 16 | 9522886537489 |
| 17 | 66660205762417 |
| 18 | 466621440336913 |
| 19 | 3266350082358387 |
| 20 | 22864450576508703 |