Search: id:A128330
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%I A128330
%S A128330 1,2,2,2,3,2,3,3,3,3,4,4,5,4,4,4,5,5,6,6,6,6,7,6,6,6,6,6,7,7,8,8,8,8,8,
%T A128330 8,9,9,9,9,10,10,11,10,10,10,11,11,11,11,11,11,12,12,12,12,12,12,13,12,
%U A128330 13,13,13,13,13,13,14,14,14,14,15,15,16,16,16,16,16,16,17,16,16,16,17
%N A128330 a(1)=1. a(n) = number of positive numbers <= n that are coprime to the 
               product of the first n-1 terms of this sequence.
%H A128330 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%e A128330 The first 6 terms of the sequence are 1,2,2,2,3,2,3. The number of positive 
               integers <= 7 that are coprime to 1, 2 and 3 is three, these integers 
               being 1, 5 and 7. So a(7) = 3.
%p A128330 a[1]:=1: for n from 2 to 105 do a[n]:=0: for j from 1 to n do if igcd(j,
               product(a[i],i=1..n-1))=1 then a[n]:=a[n]+1 else fi od: od: seq(a[n],
               n=1..105); - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 22 2007
%Y A128330 Sequence in context: A079085 A076869 A104307 this_sequence A133801 A112310 
               A137734
%Y A128330 Adjacent sequences: A128327 A128328 A128329 this_sequence A128331 A128332 
               A128333
%K A128330 nonn
%O A128330 1,2
%A A128330 Leroy Quet May 04 2007
%E A128330 More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), May 22 2007

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