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 | 2 |
| 3 | 12 |
| 4 | 120 |
| 5 | 168 |
| 6 | 1680 |
| 7 | 2217600 |
| 8 | 2620800 |
| 9 | 7539840 |
| 10 | 2459358720 |
| 11 | 45321292800 |
| 12 | 168289228800 |
| 13 | 3854798070733209600 |
| 14 | 7300628131494297600 |
| 15 | 72805439777469235200 |
| 16 | 1670428855291340390400 |
| 17 | 101997752596918507929600 |
| 18 | 292808914099957994618880000 |