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 | 3 |
| 1 | 9 |
| 2 | 29 |
| 3 | 99 |
| 4 | 353 |
| 5 | 1299 |
| 6 | 4889 |
| 7 | 18699 |
| 8 | 72353 |
| 9 | 282339 |
| 10 | 1108649 |
| 11 | 4373499 |
| 12 | 17312753 |
| 13 | 68711379 |
| 14 | 273234809 |
| 15 | 1088123499 |
| 16 | 4338079553 |
| 17 | 17309140419 |
| 18 | 69107159369 |
| 19 | 276040692699 |
| 20 | 1102999460753 |
| 21 | 4408508961459 |
| 22 | 17623571298329 |