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 | 71 |
| 2 | 4159 |
| 3 | 32831 |
| 4 | 262151 |
| 5 | 266239 |
| 6 | 294911 |
| 7 | 2101247 |
| 8 | 18874367 |
| 9 | 134479871 |
| 10 | 1073741831 |
| 11 | 68721573887 |
| 12 | 549755813951 |
| 13 | 4398046515199 |
| 14 | 4398046543871 |
| 15 | 4398046773247 |
| 16 | 4398063288319 |
| 17 | 281474976711167 |
| 18 | 281474976743423 |
| 19 | 281474978807807 |
| 20 | 281474993487871 |
| 21 | 282024732524543 |