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 | 15 |
| 2 | 85 |
| 3 | 771 |
| 4 | 4369 |
| 5 | 65535 |
| 6 | 327685 |
| 7 | 3342387 |
| 8 | 16843009 |
| 9 | 252645135 |
| 10 | 1431655765 |
| 11 | 12884901891 |
| 12 | 73014444049 |
| 13 | 1095216660735 |
| 14 | 5519032976645 |
| 15 | 56294136361779 |
| 16 | 281479271743489 |
| 17 | 4222189076152335 |
| 18 | 23925738098196565 |