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Counting & ProbabilityChallengeIdentities and Techniques, Proved

Identities and Techniques, Proved · Challenge problem

How many ordered 55-tuples (x1,x2,x3,x4,x5)(x_1,x_2,x_3,x_4,x_5) of nonnegative integers with x1+x2+x3+x4+x5=20x_1+x_2+x_3+x_4+x_5=20 have exactly two odd entries?