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 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 63 |
| 5 | 255 |
| 6 | 495 |
| 7 | 4095 |
| 8 | 96255 |
| 9 | 98175 |
| 10 | 130815 |
| 11 | 203775 |
| 12 | 1048575 |
| 13 | 5810175 |
| 14 | 6455295 |
| 15 | 16777215 |
| 16 | 67096575 |
| 17 | 88062975 |
| 18 | 389656575 |
| 19 | 553517055 |
| 20 | 850917375 |
| 21 | 1157349375 |
| 22 | 9141354495 |
| 23 | 12826279935 |
| 24 | 22828220415 |
| 25 | 26818379775 |
| 26 | 31684427775 |
| 27 | 68719476735 |
| 28 | 242870910975 |
| 29 | 1168231038975 |