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 | 3 |
| 2 | 6 |
| 3 | 18 |
| 4 | 66 |
| 5 | 258 |
| 6 | 1026 |
| 7 | 4098 |
| 8 | 16386 |
| 9 | 65538 |
| 10 | 262146 |
| 11 | 1048578 |
| 12 | 4194306 |
| 13 | 16777218 |
| 14 | 67108866 |
| 15 | 268435458 |
| 16 | 1073741826 |
| 17 | 4294967298 |
| 18 | 17179869186 |
| 19 | 68719476738 |
| 20 | 274877906946 |
| 21 | 1099511627778 |
| 22 | 4398046511106 |
| 23 | 17592186044418 |
| 24 | 70368744177666 |