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 | 9 |
| 5 | 65 |
| 6 | 73 |
| 7 | 513 |
| 8 | 4097 |
| 9 | 4161 |
| 10 | 32769 |
| 11 | 262145 |
| 12 | 262657 |
| 13 | 2097153 |
| 14 | 16777217 |
| 15 | 16781313 |
| 16 | 134217729 |
| 17 | 1073741825 |
| 18 | 1073774593 |
| 19 | 8589934593 |
| 20 | 68719476737 |
| 21 | 68719738881 |