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 | 1 |
| 2 | 11 |
| 3 | 47 |
| 4 | 191 |
| 5 | 767 |
| 6 | 3071 |
| 7 | 12287 |
| 8 | 49151 |
| 9 | 196607 |
| 10 | 786431 |
| 11 | 3145727 |
| 12 | 12582911 |
| 13 | 50331647 |
| 14 | 201326591 |
| 15 | 805306367 |
| 16 | 3221225471 |
| 17 | 12884901887 |
| 18 | 51539607551 |
| 19 | 206158430207 |
| 20 | 824633720831 |
| 21 | 3298534883327 |
| 22 | 13194139533311 |
| 23 | 52776558133247 |
| 24 | 211106232532991 |
| 25 | 844424930131967 |