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 A173440 Number of divisors d of number n such that sigma(d) does not divide sigma(n). 2

%I

%S 0,0,0,1,0,0,0,1,1,0,0,2,0,0,0,3,0,2,0,1,0,0,0,2,1,0,1,2,0,0,0,2,0,0,

%T 0,5,0,0,0,2,0,0,0,1,2,0,0,6,1,2,0,2,0,2,0,2,0,0,0,2,0,0,1,5,0,0,0

%N Number of divisors d of number n such that sigma(d) does not divide sigma(n).

%C a(n) = A000005(n) - A173439(n). a(n) = 0 for squarefree numbers (A005117).

%e For n = 12: a(12) = 2; sigma(12) = 28, divisors of 12: 1, 2, 3, 4, 6, 12; corresponding sigma(d):1, 3, 4, 7, 12, 28; sigma(d) does not divide sigma(n) for 2 divisors d: 2 and 6.

%o (Sage) A173440 = lambda n: len([d for d in divisors(n) if not sigma(d).divides(sigma(n))]) [D. S. McNeil, Dec 8 2010]

%Y Cf. A000203, A000005, A173439.

%K nonn

%O 1,12

%A _Jaroslav Krizek_, Feb 18 2010

%E Edited and extended by _D. S. McNeil_, Dec 08 2010

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