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) |
|---|---|
| 1 | 63 |
| 2 | 1023 |
| 3 | 16383 |
| 4 | 32767 |
| 5 | 67108863 |
| 6 | 1073741823 |
| 7 | 17179869183 |
| 8 | 274877906943 |
| 9 | 8796093022207 |
| 10 | 2251799813685247 |
| 11 | 4611686018427387903 |
| 12 | 36893488147419103231 |