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 | 31 |
| 2 | 511 |
| 3 | 8191 |
| 4 | 131071 |
| 5 | 2097151 |
| 6 | 33554431 |
| 7 | 536870911 |
| 8 | 8589934591 |
| 9 | 137438953471 |
| 10 | 2199023255551 |
| 11 | 35184372088831 |
| 12 | 562949953421311 |
| 13 | 9007199254740991 |
| 14 | 144115188075855871 |
| 15 | 2305843009213693951 |
| 16 | 36893488147419103231 |
| 17 | 590295810358705651711 |
| 18 | 9444732965739290427391 |