MathDB
Changing powers of 2 in binary representation to q-powers

Source: Japanese MO Finals 1996

February 11, 2011
number theory unsolvednumber theory

Problem Statement

Let qq be a real number with 1+52<q<2\frac{1+\sqrt{5}}{2}<q<2. If a positive integer nn is represented in binary system as 2k+ak12k1++2a1+a02^k+a_{k-1}2^{k-1}+\cdots +2a_1+a_0, where ai{0,1}a_i\in\{0,1\}, define pn=qk+ak1qk1++qa1+a0.p_n=q^k+a_{k-1}q^{k-1}+\cdots +qa_1+a_0. Prove that there exist infinitely many positive integers kk with the property that there is no lNl\in\mathbb{N} such that p2k<pl<p2k+1p_{2k}<p_l< p_{2k+1} .