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 A074385 Square root of sum of divisors, when it is a square. 2

%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

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Last modified September 24 09:10 EDT 2021. Contains 347630 sequences. (Running on oeis4.)