MathCastle
Proof WritingChallengeInduction

Induction · Challenge problem

Add up the sizes of all 2102^{10} subsets of a 1010-element set. (Induct on nn: removing an element xx shows S(k+1)=2S(k)+2kS(k + 1) = 2S(k) + 2^k.) What is the total?