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 | 0 |
| 2 | 126 |
| 3 | 4032 |
| 4 | 228690 |
| 5 | 14394240 |
| 6 | 1020623940 |
| 7 | 78353170560 |
| 8 | 6393827197170 |