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 | 3 |
| 2 | 27 |
| 3 | 189 |
| 4 | 1215 |
| 5 | 7533 |
| 6 | 45927 |
| 7 | 277749 |
| 8 | 1673055 |
| 9 | 10058013 |
| 10 | 60407127 |
| 11 | 362619909 |
| 12 | 2176250895 |
| 13 | 13059099693 |
| 14 | 78359381127 |
| 15 | 470170635669 |
| 16 | 2821066860735 |
| 17 | 16926530304573 |
| 18 | 101559569247927 |
| 19 | 609358577749029 |
| 20 | 3656154953278575 |
| 21 | 21936940180024653 |