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 | 2 |
| 1 | 5 |
| 2 | 17 |
| 3 | 67 |
| 4 | 257 |
| 5 | 1031 |
| 6 | 4099 |
| 7 | 16411 |
| 8 | 65537 |
| 9 | 262147 |
| 10 | 1048583 |
| 11 | 4194319 |
| 12 | 16777259 |
| 13 | 67108879 |
| 14 | 268435459 |
| 15 | 1073741827 |
| 16 | 4294967311 |
| 17 | 17179869209 |
| 18 | 68719476767 |
| 19 | 274877906951 |
| 20 | 1099511627791 |
| 21 | 4398046511119 |
| 22 | 17592186044423 |
| 23 | 70368744177679 |
| 24 | 281474976710677 |
| 25 | 1125899906842679 |