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First hint to puzzle 106: Flying cards

There are 252 equally likely configurations of face up/face down.  We seek the number of configurations for which the sum of face up card values is divisible by 13.

Consider the generating function
f(x) = (1 + x)4(1 + x2)4...(1 + x13)4 = a0 + a1x + a2x2 ... + a364x364.

Each exponent in the generating function represents a total score, and the corresponding coefficient represents the number of ways of obtaining that score.