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 | 5 |
| 2 | 33 |
| 3 | 193 |
| 4 | 1025 |
| 5 | 5121 |
| 6 | 24577 |
| 7 | 114689 |
| 8 | 524289 |
| 9 | 2359297 |
| 10 | 10485761 |
| 11 | 46137345 |
| 12 | 201326593 |
| 13 | 872415233 |
| 14 | 3758096385 |
| 15 | 16106127361 |
| 16 | 68719476737 |
| 17 | 292057776129 |
| 18 | 1236950581249 |
| 19 | 5222680231937 |
| 20 | 21990232555521 |
| 21 | 92358976733185 |