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 | 11 |
| 1 | 23 |
| 2 | 71 |
| 3 | 263 |
| 4 | 1031 |
| 5 | 4103 |
| 6 | 16391 |
| 7 | 65543 |
| 8 | 262151 |
| 9 | 1048583 |
| 10 | 4194311 |
| 11 | 16777223 |
| 12 | 67108871 |
| 13 | 268435463 |
| 14 | 1073741831 |
| 15 | 4294967303 |
| 16 | 17179869191 |
| 17 | 68719476743 |
| 18 | 274877906951 |
| 19 | 1099511627783 |
| 20 | 4398046511111 |
| 21 | 17592186044423 |
| 22 | 70368744177671 |
| 23 | 281474976710663 |
| 24 | 1125899906842631 |