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 | 0 |
| 2 | 3 |
| 3 | 9 |
| 4 | 33 |
| 5 | 99 |
| 6 | 315 |
| 7 | 945 |
| 8 | 2883 |
| 9 | 8649 |
| 10 | 26091 |
| 11 | 78273 |
| 12 | 235233 |
| 13 | 705699 |
| 14 | 2118339 |
| 15 | 6355017 |
| 16 | 19068729 |
| 17 | 57206187 |
| 18 | 171629595 |
| 19 | 514888785 |
| 20 | 1544699313 |
| 21 | 4634097939 |
| 22 | 13902392691 |
| 23 | 41707178073 |
| 24 | 125121830427 |
| 25 | 375365491281 |