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 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 156 |
| 7 | 7013320 |
| 8 | 29281354514767168 |
| 9 | 234431745534048922731115555415680 |
| 10 | 453456943706240925312368435237969462391555337386758635520 |