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%I #8 Jan 15 2022 13:59:38
%S 0,1,1,1,1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,0,1,1,1,0,1,1,1,1,1,1,
%T 2,2,1,1,2,0,1,1,1,1,1,1,1,1,1,2,1,1,1,0,2,1,2,1,1,1,1,1,2,1,2,1,1,1,
%U 1,2,1,1,1,1,2,1,2,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,2,1,1,0,1,2,1,2,1,1,1,1,2
%N Number of prime divisors of n that do not divide sigma(n); a(1) = 0.
%H Antti Karttunen, <a href="/A336387/b336387.txt">Table of n, a(n) for n = 1..65537</a>
%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F a(n) = Sum_{p over distinct primes dividing n} [sigma(n) != 0 mod p].
%t Table[Length[Select[FactorInteger[n][[All,1]],Mod[DivisorSigma[ 1,n],#]!= 0&]],{n,110}] (* _Harvey P. Dale_, Jan 15 2022 *)
%o (PARI) A336387(n) = if(1==n,0,my(s=sigma(n)); #select(p -> (s%p), factor(n)[, 1]));
%Y Cf. A175200 (positions of zeros).
%Y Cf. also A173438, A336352, A336388.
%K nonn
%O 1,21
%A _Antti Karttunen_, Jul 25 2020
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