MathDB
IMO Shortlist 2014 N4

Source:

July 11, 2015
floor functionIMO Shortlistnumber theorySequenceParityIMO Shortlist 2014Hi

Problem Statement

Let n>1n > 1 be a given integer. Prove that infinitely many terms of the sequence (ak)k1(a_k )_{k\ge 1}, defined by ak=nkk,a_k=\left\lfloor\frac{n^k}{k}\right\rfloor, are odd. (For a real number xx, x\lfloor x\rfloor denotes the largest integer not exceeding xx.)
Proposed by Hong Kong