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 | 41494252800 |
| 7 | 6923871998400 |
| 8 | 983114244363720 |
| 9 | 139528504017728552 |