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 | 5 |
| 2 | 7 |
| 3 | 19 |
| 4 | 67 |
| 5 | 1027 |
| 6 | 4099 |
| 7 | 65539 |
| 8 | 262147 |
| 9 | 4194307 |
| 10 | 268435459 |
| 11 | 1073741827 |
| 12 | 68719476739 |
| 13 | 1099511627779 |
| 14 | 4398046511107 |
| 15 | 70368744177667 |
| 16 | 4503599627370499 |
| 17 | 288230376151711747 |
| 18 | 1152921504606846979 |
| 19 | 73786976294838206467 |
| 20 | 1180591620717411303427 |
| 21 | 4722366482869645213699 |