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 | -1 |
| 2 | 7 |
| 3 | 47 |
| 4 | 223 |
| 5 | 959 |
| 6 | 3967 |
| 7 | 16127 |
| 8 | 65023 |
| 9 | 261119 |
| 10 | 1046527 |
| 11 | 4190207 |
| 12 | 16769023 |
| 13 | 67092479 |
| 14 | 268402687 |
| 15 | 1073676287 |
| 16 | 4294836223 |
| 17 | 17179607039 |
| 18 | 68718952447 |
| 19 | 274876858367 |
| 20 | 1099509530623 |
| 21 | 4398042316799 |
| 22 | 17592177655807 |
| 23 | 70368727400447 |
| 24 | 281474943156223 |
| 25 | 1125899839733759 |