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 | 9 |
| 3 | 39 |
| 4 | 183 |
| 5 | 833 |
| 6 | 3629 |
| 7 | 15291 |
| 8 | 63051 |
| 9 | 256605 |
| 10 | 1036401 |
| 11 | 4167815 |
| 12 | 16720031 |
| 13 | 66986169 |
| 14 | 268173525 |
| 15 | 1073185011 |
| 16 | 4293787923 |
| 17 | 17177379125 |
| 18 | 68714234201 |
| 19 | 274866897279 |
| 20 | 1099488559527 |
| 21 | 4397998277073 |
| 22 | 17592085381629 |
| 23 | 70368534463019 |
| 24 | 281474540503643 |
| 25 | 1125899000873613 |