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 | 4 |
| 1 | 7 |
| 2 | 19 |
| 3 | 67 |
| 4 | 259 |
| 5 | 1027 |
| 6 | 4099 |
| 7 | 16387 |
| 8 | 65539 |
| 9 | 262147 |
| 10 | 1048579 |
| 11 | 4194307 |
| 12 | 16777219 |
| 13 | 67108867 |
| 14 | 268435459 |
| 15 | 1073741827 |
| 16 | 4294967299 |
| 17 | 17179869187 |
| 18 | 68719476739 |
| 19 | 274877906947 |
| 20 | 1099511627779 |
| 21 | 4398046511107 |
| 22 | 17592186044419 |
| 23 | 70368744177667 |
| 24 | 281474976710659 |