MathDB
IZhO 2024, P3

Source:

January 9, 2024
number theory

Problem Statement

Positive integer dd is not perfect square. For each positive integer nn, let s(n)s(n) denote the number of digits 11 among the first nn digits in the binary representation of d\sqrt{d} (including the digits before the point). Prove that there exists an integer AA such that s(n)>2n2s(n)>\sqrt{2n}-2 for all integers nAn\ge A