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 | 4 |
| 2 | 0 |
| 3 | 13 |
| 4 | 0 |
| 5 | 47 |
| 6 | 0 |
| 7 | 311 |
| 8 | 0 |
| 9 | 1944 |
| 10 | 0 |
| 11 | 12811 |
| 12 | 0 |
| 13 | 84424 |
| 14 | 0 |
| 15 | 575612 |
| 16 | 0 |
| 17 | 4078451 |
| 18 | 0 |
| 19 | 28998777 |
| 20 | 0 |
| 21 | 205852759 |
| 22 | 0 |