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 | 1 |
| 2 | 9 |
| 3 | 31 |
| 4 | 129 |
| 5 | 511 |
| 6 | 2049 |
| 7 | 8191 |
| 8 | 32769 |
| 9 | 131071 |
| 10 | 524289 |
| 11 | 2097151 |
| 12 | 8388609 |
| 13 | 33554431 |
| 14 | 134217729 |
| 15 | 536870911 |
| 16 | 2147483649 |
| 17 | 8589934591 |
| 18 | 34359738369 |
| 19 | 137438953471 |
| 20 | 549755813889 |
| 21 | 2199023255551 |
| 22 | 8796093022209 |
| 23 | 35184372088831 |
| 24 | 140737488355329 |
| 25 | 562949953421311 |