%I #10 Feb 03 2019 12:40:11

%S 1,1,2,2,4,2,6,2,8,2,10,2,10,2,14,2,16,2,16,2,20,2,19,23,4,4,26,4,27,

%T 26,27,31,7,33,9,27,11,35,13,39,14,13,14,16,44,9,15,33,19,38,50,11,21,

%U 37,22,11,24,24,58,24,54,24,45,63,26,25,26,27,15,60,70,29,16,14,74,14,59

%N a(1)=1; a(n) = number of earlier terms of the sequence that are coprime to (n+a(n-1)).

%e 13 + a(12) = 15. There are 10 terms among a(1),a(2)..,a(12) that are coprime to 15. (These terms are a(1),a(2),a(3),a(4),a(5),a(6),a(8),a(9), a(10) and a(12).) So a(13) = 10.

%p a[1]:=1: for n from 2 to 100 do ct:=0: for j from 1 to n-1 do if igcd(a[j],n+a[n-1])=1 then ct:=ct+1 else fi od: a[n]:=ct: od: seq(a[n],n=1..100); # _Emeric Deutsch_, Apr 17 2007

%Y Cf. A129456.

%K nonn

%O 1,3

%A _Leroy Quet_, Apr 16 2007

%E More terms from _Emeric Deutsch_, Apr 17 2007