MathDB
Partition of natural numbers by 2-element sets

Source: Iran 2nd round 2012-Day2-P4

May 1, 2012
inequalitiescombinatorics proposedcombinatorics

Problem Statement

a) Do there exist 22-element subsets A1,A2,A3,...A_1,A_2,A_3,... of natural numbers such that each natural number appears in exactly one of these sets and also for each natural number nn, sum of the elements of AnA_n equals 1391+n1391+n?
b) Do there exist 22-element subsets A1,A2,A3,...A_1,A_2,A_3,... of natural numbers such that each natural number appears in exactly one of these sets and also for each natural number nn, sum of the elements of AnA_n equals 1391+n21391+n^2?
Proposed by Morteza Saghafian