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 | 97 |
| 4 | 699 |
| 5 | 5313 |
| 6 | 41689 |
| 7 | 334215 |
| 8 | 2721411 |
| 9 | 22423737 |
| 10 | 186497325 |
| 11 | 1562826195 |
| 12 | 13178010405 |
| 13 | 111700773135 |
| 14 | 951026829255 |
| 15 | 8128169277897 |
| 16 | 69701329848051 |
| 17 | 599462375836185 |
| 18 | 5169038197383789 |
| 19 | 44674793959777443 |
| 20 | 386916485124220929 |
| 21 | 3357265884164614707 |