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 | 1 |
| 3 | 6 |
| 4 | 27 |
| 5 | 108 |
| 6 | 405 |
| 7 | 1458 |
| 8 | 5103 |
| 9 | 17496 |
| 10 | 59049 |
| 11 | 196830 |
| 12 | 649539 |
| 13 | 2125764 |
| 14 | 6908733 |
| 15 | 22320522 |
| 16 | 71744535 |
| 17 | 229582512 |
| 18 | 731794257 |
| 19 | 2324522934 |
| 20 | 7360989291 |
| 21 | 23245229340 |
| 22 | 73222472421 |
| 23 | 230127770466 |
| 24 | 721764371007 |
| 25 | 2259436291848 |