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 | 1 |
| 2 | 1 |
| 3 | 0 |
| 4 | 1 |
| 5 | 0 |
| 6 | 3 |
| 7 | 0 |
| 8 | 12 |
| 9 | 2 |
| 10 | 55 |
| 11 | 22 |
| 12 | 278 |
| 13 | 182 |
| 14 | 1506 |
| 15 | 1378 |
| 16 | 8595 |
| 17 | 10040 |
| 18 | 51134 |
| 19 | 71814 |
| 20 | 314693 |
| 21 | 509200 |