MathDB
Inequality

Source: Polish National Olympiad 2015 2nd round, 2nd problem

March 3, 2015
inequalities

Problem Statement

Let AA be an integer and A>1A>1. Let a1=AAa_{1}=A^{A}, an+1=Aana_{n+1}=A^{a_{n}} and b1=AA+1b_{1}=A^{A+1}, bn+1=2bnb_{n+1}=2^{b_{n}}, n=1,2,3,...n=1, 2, 3, .... Prove that an<bna_{n}<b_{n} for each nn.