Search: id:A103340
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%I A103340
%S A103340 1,3,2,5,3,1,4,9,5,9,6,5,7,3,2,17,9,5,10,3,8,9,12,3,13,21,14,5,15,3,16,
%T A103340 33,4,27,12,25,19,15,14,27,21,2,22,15,1,9,24,17,25,39,6,35,27,7,18,9,20,
%U A103340 45,30,1,31,12,20,65,21,3,34,45,8,9,36,5,37,57,26,25,24,7,40,51,41,63
%N A103340 Denominator of the unitary harmonic mean (i.e. the harmonic mean of the 
               unitary divisors) of the positive integer n.
%e A103340 1,4/3,3/2,8/5,5/3,2,
%e A103340 a(8)=9 because the unitary divisors of 8 are {1,8} and 2/(1/1+1/8)=16/
               9.
%p A103340 with(numtheory): udivisors:=proc(n) local A, k: A:={}: for k from 1 to 
               tau(n) do if gcd(divisors(n)[k], n/divisors(n)[k])=1 then A:=A union 
               {divisors(n)[k]} else A:=A fi od end: utau:=n->nops(udivisors(n)): 
               usigma:=n->sum(udivisors(n)[j],j=1..nops(udivisors(n))): uH:=n->n*utau(n)/
               usigma(n):seq(denom(uH(n)),n=1..90);
%Y A103340 Cf. A103339, A099377, A099378.
%Y A103340 Sequence in context: A046227 A120842 A152178 this_sequence A106615 A130299 
               A143309
%Y A103340 Adjacent sequences: A103337 A103338 A103339 this_sequence A103341 A103342 
               A103343
%K A103340 frac,nonn
%O A103340 1,2
%A A103340 Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 31 2005

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