(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

How many non- empty subsets of {1,2,3...,15} have the following two properties?

1) No two consecutive integers belong to S.

2)If S contains K elements, then S contains no number less than K .

2. Relevant equations

choosing identities, not sure which one

3. The attempt at a solution

Tried casework, but I dont understand how the solution gets

n-k+1 choose k

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# Homework Help: Combinatorics intense question!

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