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PutnamSuperchallengeIntegrals I: Feynman's Trick

Integrals I: Feynman's Trick · Superchallenge problem

Determine the number of integers NN with 1≤N≤2001 \le N \le 200 for which the equation x2+y2+z2=Nx^2 + y^2 + z^2 = N has a solution in integers with x,y,zx, y, z all odd.