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 | 0 |
| 2 | 1 |
| 3 | 7 |
| 4 | 31 |
| 5 | 2047 |
| 6 | 32767 |
| 7 | 131071 |
| 8 | 536870911 |
| 9 | 576460752303423487 |
| 10 | 154742504910672534362390527 |
| 11 | 40564819207303340847894502572031 |
| 12 | 42535295865117307932921825928971026431 |