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 | 20 |
| 3 | 1680 |
| 4 | 369600 |
| 5 | 168168000 |
| 6 | 137225088000 |
| 7 | 67280653440000 |
| 8 | 22859094527068800 |
| 9 | 6325233865588881600 |