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 | 0 |
| 3 | 1 |
| 4 | 5 |
| 5 | 18 |
| 6 | 56 |
| 7 | 163 |
| 8 | 459 |
| 9 | 1286 |
| 10 | 3640 |
| 11 | 10479 |
| 12 | 30659 |
| 13 | 90738 |
| 14 | 270092 |
| 15 | 804833 |
| 16 | 2393929 |
| 17 | 7098790 |
| 18 | 20984188 |
| 19 | 61872587 |
| 20 | 182130495 |
| 21 | 535698422 |
| 22 | 1575478728 |
| 23 | 4635125097 |
| 24 | 13645054833 |
| 25 | 40196623234 |
| 26 | 118493318904 |
| 27 | 349506908369 |
| 28 | 1031426887149 |