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 | 31 |
| 3 | 191 |
| 4 | 1023 |
| 5 | 5119 |
| 6 | 24575 |
| 7 | 114687 |
| 8 | 524287 |
| 9 | 2359295 |
| 10 | 10485759 |
| 11 | 46137343 |
| 12 | 201326591 |
| 13 | 872415231 |
| 14 | 3758096383 |
| 15 | 16106127359 |
| 16 | 68719476735 |
| 17 | 292057776127 |
| 18 | 1236950581247 |
| 19 | 5222680231935 |
| 20 | 21990232555519 |
| 21 | 92358976733183 |
| 22 | 387028092977151 |
| 23 | 1618481116086271 |
| 24 | 6755399441055743 |