HMIC #0k8x

HMICHard

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Understand the scale

Scale 0.5: Easiest math competition problems, often solvable even for early middle school students without experience. 1: Problems strictly for beginners, often at a moderate middle school level. 1.5: Problems for stronger beginner students, on the level of the middling problems in most middle school contests. 2: For motivated beginners, harder questions from the previous categories. 2.5: More advanced beginner problems, hardest questions from previous categories. 3: Early intermediate problems that require more creative thinking. 3.5: Tougher early intermediate problems that consistently stretch into higher-level creative thinking or conceptual knowledge. 4: Intermediate-level problems. 4.5: Upper intermediate problems approaching the upper bound for non-invitational sprint math competitions. 5: More difficult AIME problems or simple proof-based Olympiad-style problems. 6: High-level AIME-styled questions or introductory Olympiad-level questions. 7: Tougher Olympiad-level questions, may require more technical knowledge. 8: High-level Olympiad-level questions. 9: Expert Olympiad-level questions. 9.5: The hardest problems appearing on Olympiads which the strongest students could reasonably solve. 10: Historically notorious problems, generally unsuitable for even very hard competitions because they are exceedingly tedious, long, and difficult.

Recurrence relationsVieta's formulasRoots of unityMultiplicative orderφ (Euler's totient)

Problem

Problem:

Let $p=2017$ be a prime and $\mathbb{F}_p$ be the integers modulo $p$ . A function $f: \mathbb{Z} \rightarrow \mathbb{F}_p$ is called good if there is $\alpha \in \mathbb{F}_p$ with $\alpha \not \equiv 0 (\bmod p)$ such that

f(x) f(y) = f(x+y) + \alpha^{y} f(x-y) \quad (\bmod p)

for all $x, y \in \mathbb{Z}$ . How many good functions are there that are periodic with minimal period $2016$ ?

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