MathDB
Congruence relation with binomial coefficients

Source: Netherlands IMO Team Selection Test 2013

October 21, 2014
modular arithmeticnumber theory unsolvednumber theory

Problem Statement

Determine all positive integers n2n\ge 2 satisfying i+j(ni)+(nj)(mod2)i+j\equiv\binom ni +\binom nj \pmod{2} for all ii and jj with 0ijn0\le i\le j\le n.