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Berkeley Math Circle: Monthly Contest 7 #0hun

Berkeley Math Circle: Monthly Contest 7Hard

From module Induction on olympiad

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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.
Induction / smoothingIntegers

Problem

Problem: Prove that there exist pairwise distinct positive integers a0,a1,a2,…,a1000a_{0}, a_{1}, a_{2}, \ldots, a_{1000} such that

a0!=a1! a2! … a1000!a_{0}! = a_{1}!\, a_{2}!\, \ldots\, a_{1000}!

Here n!=1×2×⋯×nn! = 1 \times 2 \times \cdots \times n as usual.

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