MathDB
2^(n-1) | n! if and only if n is a power of 2 [Canada 1985]

Source:

September 30, 2011
floor functionlogarithmsinequalitiesnumber theoryprime factorization

Problem Statement

Prove that 2n−12^{n - 1} divides n!n! if and only if n=2k−1n = 2^{k - 1} for some positive integer kk.
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