7^a - 3^b divides a^4 + b^2 (from IMO Shortlist 2007)
Source: ISL 2007, N1, VAIMO 2008, P4
April 21, 2008
DivisibilityIMO Shortlistnumber theory
Problem Statement
Find all pairs of natural numbers such that 7^a \minus{} 3^b divides a^4 \plus{} b^2.Author: Stephan Wagner, Austria