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 | 1 |
| 2 | 5040 |
| 3 | 403291461126605635584000000 |
| 4 | 1982608315404440064116146708361898137544773690227268628106279599612729753600000000000000 |