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%I #4 Sep 08 2020 22:01:31
%S 1,1,1,2,2,1,1,2,2,3,1,2,1,1,3,3,1,2,1,4,1,1,1,2,3,1,2,2,1,4,1,3,1,2,
%T 2,4,1,1,2,5,1,1,1,2,6,1,1,3,2,4,1,2,1,2,2,2,1,1,1,6,1,1,2,4,3,1,1,4,
%U 1,3,1,4,1,1,4,2,1,3,1,6,3,1,1,2,2,1,1,2,1,8,1,2,1,1,2
%N Number of ways that the divisors of 2n can be written as the sum of the squares of two other divisors of 2n (not necessarily distinct).
%C a(n) >= 1 since 2n always has 1 and 2 as divisors with 1^2 + 1^2 = 2.
%F a(n) = Sum_{d1|(2*n), d2|(2*n), d3|(2*n), d1<=d2<=d3} [d1^2 + d2^2 = d3], where [ ] is the Iverson bracket.
%e a(10) = 3; The divisors of 2*10 = 20 are {1,2,4,5,10,20}. Since 1^2 + 1^2 = 2, 1^2 + 2^2 = 5 and 2^2 + 4^2 = 20, there are 3 total ways.
%K nonn,easy
%O 1,4
%A _Wesley Ivan Hurt_, Aug 30 2020
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