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A074385
Square root of sum of divisors, when it is a square.
2
1, 2, 6, 12, 12, 11, 12, 12, 12, 18, 24, 18, 16, 18, 24, 24, 24, 20, 24, 24, 28, 24, 24, 31, 30, 24, 36, 24, 24, 36, 32, 28, 36, 36, 30, 36, 36, 42, 36, 42, 32, 48, 36, 48, 42, 42, 40, 42, 60, 56, 48, 48, 42, 36, 62, 36, 36, 48, 40, 60, 48, 42, 48, 40, 48, 60, 48, 56, 60, 48
OFFSET
1,2
LINKS
FORMULA
a(n) = sqrt(A000203(A006532(n))).
MATHEMATICA
Select[Sqrt[DivisorSigma[1, Range@1800]], IntegerQ] (* Ivan Neretin, Jun 05 2015 *)
PROG
(PARI) lista(nn) = {for (n=1, nn, if (issquare(s=sigma(n)), print1(sqrtint(s), ", ")); ); } \\ Michel Marcus, Dec 18 2013
CROSSREFS
Sequence in context: A379518 A130503 A278232 * A057340 A092427 A379622
KEYWORD
nonn,look
AUTHOR
Labos Elemer, Aug 22 2002
STATUS
approved