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 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 1961256 |
| 5 | 4730523156632595024 |
| 6 | 14714642085645788453359573419196194379200 |
| 7 | 141671570521482692258866117076218807527442238234361038404229857860891009480 |