Question

Find the number of permutations of first N natural numbers such that given conditions should be satisfied. The given conditions can be something like this
x and y not occurs consecutively
p and q not occurs consecutively
r and s not occurs consecutively
..etc
Discussion part 1 : http://openstudy.com/study#/updates/568a1e3de4b0f8b822a18485

Answer 1

n=4 not connected ones are=>
1, 2
2, 3
3, 4