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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 5 |
| 5 | 21 |
| 6 | 71 |
| 7 | 255 |
| 8 | 961 |
| 9 | 3630 |
| 10 | 13973 |
| 11 | 53938 |
| 12 | 209641 |
| 13 | 815784 |
| 14 | 3183642 |
| 15 | 12439291 |
| 16 | 48686549 |
| 17 | 190787588 |
| 18 | 748645732 |