Re: Number of permutations

Quote:

Originally Posted by

**alexmahone** In how many ways can the elements of [n] be permuted so that the sum of every two consecutive elements in the permutation is odd?

[n] is the set of integers from 1 to n.

**My attempt:**
If n is even:

If n is odd, we

*must* start with an odd element:

I agree with you as far as that goes.

But in is odd it should be: because start with an odd and alternate

Re: Number of permutations

Quote:

Originally Posted by

**Plato** I agree with you as far as that goes.

But in is odd it should be: because start with an odd and alternate

Actually, that's exactly what I got. But there was a problem with the latex (which I've now fixed).