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Problem 45424. Amicable pair

Amicable numbers are two different numbers such that the sum of the proper divisors of each is equal to the other number.

For example,

 220 = 1, 2, 4, 5, 10, 11, 20, 22, 44, 55, 110  ; sum =284
 284 = 1, 2, 4, 71, 142  ; sum =220

So, 220 & 284 make an amicable pair.

Find the number of such pairs within n.

https://oeis.org/A259180

Solve

Solution Stats

60.0% Correct | 40.0% Incorrect
Last Solution submitted on Apr 08, 2020

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number theory