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 | 26 |
| 3 | 252 |
| 4 | 3368 |
| 5 | 58810 |
| 6 | 1290930 |
| 7 | 34604844 |
| 8 | 1107490596 |