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%I #9 Feb 03 2019 07:06:17
%S 1,1,2,5,9,8,17,13,8,19,21,20,47,31,14,37,39,28,67,43,20,53,57,35,58,
%T 73,53,27,41,44,67,69,50,127,83,35,52,111,125,76,103,85,56,129,155,91,
%U 74,123,149,74,101,105,116,233,111,85,113,76,123,187,107,71,62,131,133,80
%N a(0)=a(1)=1. a(n) = the n-th integer from among those positive integers coprime to (a(n-1)*a(n-2)).
%e a(4)*a(5) = 72. So a(6) = the sixth integer from among those positive integers coprime to 72 (i.e., the sixth integer in the sequence 1,5,7,11,13,17,19,23,25,...). So a(6) = 17.
%p a[0]:=1: a[1]:=1: for n from 2 to 80 do ct:=0: A:={}: for i from 1 while ct<=n do if igcd(i,a[n-1]*a[n-2])=1 then A:=A union {i}: ct:=ct+1 else ct:=ct: fi: od: a[n]:=A[n] od: seq(a[n],n=0..80); # _Emeric Deutsch_, Apr 14 2007
%Y Cf. A129141.
%K nonn
%O 0,3
%A _Leroy Quet_, Mar 30 2007
%E More terms from _Emeric Deutsch_, Apr 14 2007
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