%I
%S 1,2,6,12,12,11,12,12,12,18,24,18,16,18,24,24,24,20,24,24,28,24,24,31,
%T 30,24,36,24,24,36,32,28,36,36,30,36,36,42,36,42,32,48,36,48,42,42,40,
%U 42,60,56,48,48,42,36,62,36,36,48,40,60,48,42,48,40,48,60,48,56,60,48
%N Square root of sum of divisors, when it is a square.
%H Ivan Neretin, <a href="/A074385/b074385.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = sqrt(A000203(A006532(n))).
%t Select[Sqrt[DivisorSigma[1, Range@1800]], IntegerQ] (* _Ivan Neretin_, Jun 05 2015 *)
%o (PARI) lista(nn) = {for (n=1, nn, if (issquare(s=sigma(n)), print1(sqrtint(s), ", ")););} \\ _Michel Marcus_, Dec 18 2013
%Y Cf. A000203, A006532.
%K nonn,look
%O 1,2
%A _Labos Elemer_, Aug 22 2002
