An Activation-Code Sequence

Problem

Consider the sequence 1,1,2,1,2,4,1,2,4,8,1,2,4,8,16,1,1,2,1,2,4,1,2,4,8,1,2,4,8,16,\dots, where the first term is 202^0, the next two terms are 20,212^0,2^1, the next three are 20,21,222^0,2^1,2^2, and so on. Find the smallest integer N>100N>100 such that the sum of the first NN terms of the sequence is a power of 22.

Answer

Solution

Difficulty7/10
TopicsGeometric Progression, algebra, sequences, Casework

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