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 | 5 |
| 2 | 10 |
| 3 | 120 |
| 4 | 280840 |
| 5 | 3691654113991480 |
| 6 | 8385167839605753859676710992399730619003333960 |