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 | 7 |
| 2 | 61 |
| 3 | 505 |
| 4 | 4081 |
| 5 | 32737 |
| 6 | 262081 |
| 7 | 2097025 |
| 8 | 16776961 |
| 9 | 134217217 |
| 10 | 1073740801 |
| 11 | 8589932545 |
| 12 | 68719472641 |
| 13 | 549755805697 |
| 14 | 4398046494721 |
| 15 | 35184372056065 |
| 16 | 281474976645121 |
| 17 | 2251799813554177 |
| 18 | 18014398509219841 |
| 19 | 144115188075331585 |