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%I #13 Aug 27 2022 04:08:42
%S 1,1,3,5,8,13,15,16,31,19,11,13,15,29,28,39,61,29,19,21,40,97,57,37,
%T 41,26,59,61,29,31,33,53,56,81,121,59,40,97,99,65,92,119,111,86,139,
%U 93,73,76,105,227,109,52,115,151,72,169,185,81,113,89,61,63,110,307,177,100
%N a(1)=a(2)=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) = 40. So a(6) = the sixth integer from among those positive integers coprime to 40 (i.e., the sixth integer in the sequence 1,3,7,9,11,13,17,19,21,23,...). So a(6) = 13.
%p a[1]:=1: a[2]:=1: for n from 3 to 80 do A:={}: for i from 1 to 500 do if gcd(i,a[n-1]*a[n-2])=1 then A:=A union {i} else fi od: a[n]:=A[n]: od: seq(a[n],n=1..80); # _Emeric Deutsch_, Apr 12 2007
%Y Cf. A129140.
%K nonn
%O 1,3
%A _Leroy Quet_, Mar 30 2007
%E More terms from _Emeric Deutsch_, Apr 12 2007
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