MathDB
f(n)=f(n-1)+1

Source: Problem 3, Brazilian MO 2015

October 20, 2015
number theory proposednumber theoryprime factorization

Problem Statement

Given a natural n>1n>1 and its prime fatorization n=p1α1p2α2pkαkn=p_1^{\alpha 1}p_2^{\alpha_2} \cdots p_k^{\alpha_k}, its false derived is defined by f(n)=α1p1α11α2p2α21...αkpkαk1.f(n)=\alpha_1p_1^{\alpha_1-1}\alpha_2p_2^{\alpha_2-1}...\alpha_kp_k^{\alpha_k-1}. Prove that there exist infinitely many naturals nn such that f(n)=f(n1)+1f(n)=f(n-1)+1.