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Consider cubes of edge length 5 composed of 125 cubes

Source: German TST 5, P1, 2009

July 18, 2009
geometry3D geometryalgebra unsolvedalgebra

Problem Statement

Consider cubes of edge length 5 composed of 125 cubes of edge length 1 where each of the 125 cubes is either coloured black or white. A cube of edge length 5 is called "big", a cube od edge length is called "small". A posititve integer n n is called "representable" if there is a big cube with exactly n n small cubes where each row of five small cubes has an even number of black cubes whose centres lie on a line with distances 1,2,3,4 1,2,3,4 (zero counts as even number). (a) What is the smallest and biggest representable number? (b) Construct 45 representable numbers.