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2022 MMATHS Individual p8 - sum of gcd of 64 pairs

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October 1, 2023
number theorygreatest common divisorMMATHS

Problem Statement

Let S={1,2,3,5,6,10,15,30}S = \{1, 2, 3, 5, 6, 10, 15, 30\}. For each of the 6464 ordered pairs (a,b)(a, b) of elements of SS, AJ computes gcd(a,b)gcd(a, b). They then sum all of the numbers they computed. What is AJ’s sum?
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