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 | 0 |
| 1 | 6 |
| 2 | 30 |
| 3 | 126 |
| 4 | 510 |
| 5 | 2046 |
| 6 | 8190 |
| 7 | 32766 |
| 8 | 131070 |
| 9 | 524286 |
| 10 | 2097150 |
| 11 | 8388606 |
| 12 | 33554430 |
| 13 | 134217726 |
| 14 | 536870910 |
| 15 | 2147483646 |
| 16 | 8589934590 |
| 17 | 34359738366 |
| 18 | 137438953470 |
| 19 | 549755813886 |
| 20 | 2199023255550 |
| 21 | 8796093022206 |
| 22 | 35184372088830 |