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 | 4 |
| 3 | 56 |
| 4 | 2800 |
| 5 | 509600 |
| 6 | 342451200 |
| 7 | 858867609600 |
| 8 | 8105992499404800 |
| 9 | 289789231853721600000 |
| 10 | 39450746867638243737600000 |
| 11 | 20541057076054410196318617600000 |
| 12 | 41055903763279774965226732643942400000 |
| 13 | 315984464183472044352469495097074620825600000 |