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%I #9 Aug 22 2020 12:50:34
%S 2,5,6,10,8,21,10,19,16,29,14,46,16,37,36,36,20,61,22,64,46,53,26,91,
%T 34,61,44,82,32,141,34,69,66,77,64,136,40,85,76,127,44,181,46,118,106,
%U 101,50,176,60,133,96,136,56,173,92,163,106,125,62,316,64,133,136,134,106,261,70
%N Sum of the coordinates of all relatively prime pairs of divisors of n, (d1,d2), such that d1 <= d2.
%F a(n) = Sum_{i|n, k|n, i<=k, gcd(i,k)=1} (i+k).
%e a(4) = 10; There are 3 divisors of 4: {1,2,4}. If we list the relatively prime pairs (d1,d2), where d1 <= d2, we get (1,1), (1,2), (1,4). The sum of the coordinates from all pairs is 1+1+1+2+1+4 = 10.
%e a(5) = 8; There are 2 divisors of 5: {1,5}. The relatively prime pairs (d1,d2), where d1 <= d2 are: (1,1) and (1,5). The sum of the coordinates is then 1+1+1+5 = 8.
%t Table[Sum[Sum[(i + k) KroneckerDelta[GCD[i, k], 1] (1 - Ceiling[n/k] + Floor[n/k]) (1 - Ceiling[n/i] + Floor[n/i]), {i, k}], {k, n}], {n, 100}]
%o (PARI) a(n) = my(d = divisors(n)); sum(i=1, #d, sum(j=1, i, if (gcd(d[i],d[j])==1, d[i]+d[j]))); \\ _Michel Marcus_, Aug 22 2020
%Y Cf. A018892, A337246.
%K nonn,easy
%O 1,1
%A _Wesley Ivan Hurt_, Aug 21 2020
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