MathDB
Sum divisible by 3

Source: Problem 6, Polish NO 1990

September 30, 2005
modular arithmeticnumber theory unsolvednumber theory

Problem Statement

Prove that for all integers n>2n > 2, 3i=0[n/3](1)iCn3i 3| \sum\limits_{i=0}^{[n/3]} (-1)^i C _n ^{3i}