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) |
|---|---|
| 2 | 2 |
| 3 | 4 |
| 4 | 8 |
| 5 | 28 |
| 6 | 352 |
| 7 | 15761240 |
| 8 | 16224999167235166704456 |
| 9 | 84575066435667906978109556015360727955214108828131762704 |