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%I #15 Jul 01 2022 05:25:45
%S 1,1,1,1,1,1,1,1,2,1,1,1,1,1,2,1,1,2,1,1,2,1,1,1,2,1,3,1,1,2,1,1,2,1,
%T 2,2,1,1,2,1,1,2,1,1,4,1,1,1,2,2,2,1,1,3,2,1,2,1,1,2,1,1,4,1,2,2,1,1,
%U 2,2,1,2,1,1,4,1,2,2,1,1
%N Number of odd nonprimes dividing n.
%H G. C. Greubel, <a href="/A033272/b033272.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = A001227(n) - A005087(n). - _Amiram Eldar_, Jul 01 2022
%t Table[Length[Select[Divisors[n],OddQ[#]&&!PrimeQ[#]&]],{n,80}] (* _Harvey P. Dale_, May 06 2012 *)
%t a[n_] := DivisorSigma[0, n/2^IntegerExponent[n, 2]] - PrimeNu[n] + If[OddQ[n], 0, 1]; Array[a, 100] (* _Amiram Eldar_, Jul 01 2022 *)
%o (PARI) a(n) = sumdiv(n, d, (d%2) && !isprime(d)); \\ _Michel Marcus_, May 05 2017
%Y Cf. A001227 (with odd divisors), A005087, A033273 (with nonprime divisors).
%K nonn
%O 1,9
%A _N. J. A. Sloane_
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