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 A099042 Number of badly sieved (A066680) divisors of n. 5

%I

%S 0,1,1,1,1,2,1,2,1,2,1,3,1,2,2,2,1,3,1,2,2,2,1,4,1,2,2,2,1,4,1,2,2,2,

%T 2,4,1,2,2,3,1,3,1,2,3,2,1,4,1,3,2,2,1,4,2,3,2,2,1,5,1,2,3,2,2,3,1,2,

%U 2,4,1,5,1,2,3,2,2,3,1,4,2,2,1,4,2,2,2,3,1,6,2,2,2,2,2,4,1,3,2,3,1,3,1,3,4

%N Number of badly sieved (A066680) divisors of n.

%C A001221(n) <= a(n) <= A000005(n).

%H Antti Karttunen, <a href="/A099042/b099042.txt">Table of n, a(n) for n = 1..65537</a>

%F a(n) = Sum_{d|n} A099104(d). - _Antti Karttunen_, Jul 02 2018

%e a(24) = #{2,3,8,12} = 4; A099043(24) = 2+3+8+12 = 25;

%e a(25) = #{5} = 1; A099043(25) = 5;

%e a(26) = #{2,13} = 2; A099043(26) = 2+13 = 15.

%o (PARI)

%o A099104(n) = if(1==n,0,my(m=1); fordiv(n,d,if((d<n)&&((d*d)>=n),m *= (1-A099104(d)))); (m));

%o A099042(n) = sumdiv(n,d,A099104(d)); \\ _Antti Karttunen_, Jul 02 2018

%Y Cf. A066680, A099104.

%K nonn

%O 1,6

%A _Reinhard Zumkeller_, Sep 23 2004

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Last modified February 21 01:29 EST 2019. Contains 320364 sequences. (Running on oeis4.)