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 | 1 |
| 3 | 3 |
| 4 | 11 |
| 5 | 33 |
| 6 | 105 |
| 7 | 315 |
| 8 | 961 |
| 9 | 2883 |
| 10 | 8697 |
| 11 | 26091 |
| 12 | 78411 |
| 13 | 235233 |
| 14 | 706113 |
| 15 | 2118339 |
| 16 | 6356243 |
| 17 | 19068729 |
| 18 | 57209865 |
| 19 | 171629595 |
| 20 | 514899771 |
| 21 | 1544699313 |
| 22 | 4634130897 |
| 23 | 13902392691 |
| 24 | 41707276809 |
| 25 | 125121830427 |
| 26 | 375365787489 |
| 27 | 1126097362467 |