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 | 13 |
| 2 | 8191 |
| 3 | 797161 |
| 4 | 22369621 |
| 5 | 305175781 |
| 6 | 2612138803 |
| 7 | 16148168401 |
| 8 | 78536544841 |
| 9 | 317733228541 |
| 10 | 1111111111111 |
| 11 | 3452271214393 |
| 12 | 9726655034461 |
| 13 | 25239592216021 |
| 14 | 61054982558011 |
| 15 | 139013933454241 |
| 16 | 300239975158033 |
| 17 | 619036127056621 |
| 18 | 1224880286215951 |
| 19 | 2336276859014281 |
| 20 | 4311578947368421 |