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 | 2 |
| 2 | 5 |
| 3 | 17 |
| 4 | 65 |
| 5 | 257 |
| 6 | 1025 |
| 7 | 4097 |
| 8 | 16385 |
| 9 | 65537 |
| 10 | 262145 |
| 11 | 1048577 |
| 12 | 4194305 |
| 13 | 16777217 |
| 14 | 67108865 |
| 15 | 268435457 |
| 16 | 1073741825 |
| 17 | 4294967297 |
| 18 | 17179869185 |
| 19 | 68719476737 |
| 20 | 274877906945 |
| 21 | 1099511627777 |
| 22 | 4398046511105 |
| 23 | 17592186044417 |
| 24 | 70368744177665 |
| 25 | 281474976710657 |
| 26 | 1125899906842625 |
| 27 | 4503599627370497 |
| 28 | 18014398509481985 |