MathDB

C2

Part of 2019 Balkan MO Shortlist

Problems(1)

5x5 arrays defined in function of 2x2 subarrays

Source: BMO 2019, Shortlist

10/1/2019
Determine the largest natural number N N having the following property: every 5×5 5\times 5 array consisting of pairwise distinct natural numbers from 1 1 to 25 25 contains a 2×2 2\times 2 subarray of numbers whose sum is, at least, N. N.
Demetres Christofides and Silouan Brazitikos
linear algebramatrixBalkannumber theory