MathDB
T_n - n is even

Source: INMO 2013

February 3, 2013
Putnaminductionfunctionfloor functioncombinatorics proposedcombinatorics

Problem Statement

Let NN be an integer greater than 11 and let TnT_n be the number of non empty subsets SS of {1,2,.....,n}\{1,2,.....,n\} with the property that the average of the elements of SS is an integer.Prove that Tn−nT_n - n is always even.
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