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 | 6 |
| 3 | 6 |
| 4 | 18 |
| 5 | 30 |
| 6 | 66 |
| 7 | 126 |
| 8 | 258 |
| 9 | 510 |
| 10 | 1026 |
| 11 | 2046 |
| 12 | 4098 |
| 13 | 8190 |
| 14 | 16386 |
| 15 | 32766 |
| 16 | 65538 |
| 17 | 131070 |
| 18 | 262146 |
| 19 | 524286 |
| 20 | 1048578 |
| 21 | 2097150 |
| 22 | 4194306 |
| 23 | 8388606 |
| 24 | 16777218 |
| 25 | 33554430 |
| 26 | 67108866 |
| 27 | 134217726 |
| 28 | 268435458 |
| 29 | 536870910 |
| 30 | 1073741826 |
| 31 | 2147483646 |