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smc

number theory senior

Problem

A sequence of numbers is defined by and for . What are the parities (evenness or oddness) of the triple of numbers , where denotes even and denotes odd?
(A)
(B)
(C)
(D)
Solution
We construct the following table: Note that and have the same parities, so the parity is periodic with period Since the remainders of are we conclude that and have the same parities, namely
Final answer
C