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 | 5040 |
| 2 | 51090942171709440000 |
| 3 | 523022617466601111760007224100074291200000000 |
| 4 | 5502622159812088949850305428800254892961651752960000000000 |