- #1
newchie
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Homework Statement
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 .
Homework Equations
choosing identities, not sure which one
The Attempt at a Solution
Tried casework, but I don't understand how the solution gets
n-k+1 choose k