Search: id:A131346
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%I A131346
%S A131346 1,2,4,7,8,10,12,14,16,18,20,21,30,43,47,62,70,80,89,95,115,123,145,152,
%T A131346 162,172,179,206,234,263,270,276,286,298,307,333,341,376,404,439,449,
%U A131346 489,507,537,557,602,635,655,690,725,749,787,812,838,863,905,920,941
%N A131346 a(1)=1. a(n) = a(n-1) + (number of the terms, from among terms a(1) through 
               a(n-1), which are coprime to sum{k=1 to n-1} a(k)).
%H A131346 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%e A131346 The sum of the first 12 terms of the sequence is 133 = 7*19.
%e A131346 There are 9 terms from among the first 12 terms of the sequence that 
               are coprime to 133 (a(1)=1, a(2)=2, a(3)=4, a(5)=8, a(6)=10, a(7)=12, 
               a(9)=16, a(10)=18, a(11)=20). So a(13)= a(12) + 9 = 30.
%p A131346 a[1] := 1; for n from 2 to 60 do ct := 0; for j to n-1 do if gcd(a[j], 
               sum(a[i], i = 1 .. n-1)) = 1 then ct := ct+1 else ct := ct end if 
               end do; a[n] := a[n-1]+ct end do; seq(a[n], n = 1 .. 60) - Emeric 
               Deutsch (deutsch(AT)duke.poly.edu), Jul 17 2007
%Y A131346 Cf. A131347.
%Y A131346 Sequence in context: A139212 A127875 A056231 this_sequence A047540 A116478 
               A047236
%Y A131346 Adjacent sequences: A131343 A131344 A131345 this_sequence A131347 A131348 
               A131349
%K A131346 nonn
%O A131346 1,2
%A A131346 Leroy Quet Jul 01 2007
%E A131346 More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu) and Joshua 
               Zucker (joshua.zucker(AT)stanfordalumni.org), Jul 17 2007

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