The problem: Find a closed form of the following sequence 0,3,2,5,4,7,6,9,8,11,10,13,12.

So I get that the odds are n-1 and the evens are n+1 and I've started the equation and so far I have $\displaystyle ((-1)^(n-1) + 1)/2 + ((-1)^n + 1)/2)$ (the first part is supposed to be (-1)^(n-1)) the first half to find the odd numbers and the second to find the even numbers.

I'm having trouble coming up with where to put the n-1 and n+1. Any help or hints is appreciated.

Thanks.