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Source: China South East Mathematical Olympiad 2016 Grade 10 Prob. 6

July 31, 2016
combinatorics

Problem Statement

Toss the coin nn times, assume that each time, only appear only head or tail Let a(n)a(n) denote number of way that head appear in multiple of 33 times among nn times Let b(n)b(n) denote numbe of way that head appear in multiple of 66 times among nn times (1)(1) Find a(2016)a(2016) and b(2016)b(2016) (2)(2) Find the number of positive integer n2016n\leq 2016 that 2b(n)a(n)02b(n)-a(n)\geq 0