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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 5 |
| 5 | 4095 |
| 6 | 4097 |
| 7 | 12291 |
| 8 | 20485 |
| 9 | 21845 |
| 10 | 16777215 |
| 11 | 16777217 |
| 12 | 16781313 |
| 13 | 50331651 |
| 14 | 50343939 |
| 15 | 83886085 |
| 16 | 83906565 |
| 17 | 89458005 |
| 18 | 89478485 |
| 19 | 68702703615 |
| 20 | 68719476735 |
| 21 | 68719476737 |
| 22 | 68736258049 |
| 23 | 206158430211 |
| 24 | 206208774147 |
| 25 | 343597383685 |
| 26 | 343602954245 |
| 27 | 343681290245 |