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%I #10 Oct 10 2019 11:39:33
%S 1,1,1,3,1,5,3,6,4,7,3,10,8,8,10,11,7,11,10,13,13,14,10,18,15,16,16,
%T 17,13,20,20,16,23,21,17,25,24,21,23,25,19,30,25,25,25,29,23,36,29,29,
%U 32,33,26,41,28,37,32,37,30,41,32,41,33,42,32,51,36,44,39,43,38,52,41,44
%N a(1)=1; for n>1, a(n) = the number of earlier terms a(k), 1<k<=n-1, such that (a(k)+n) is coprime to k.
%C The value of a(1) = 1 is arbitrary. a(1) can be any integer and the rest of the sequence would remain unchanged.
%e a(1)+11 = 12 is coprime to 1; a(5)+11 = 12 is coprime to 5; and a(8)+11 = 17 is coprime to 8. These 3 are the only cases where (a(k)+11) is coprime to k, for 1 <=k <=10. So a(11) = 3.
%t f[l_List] := Block[{n = Length[l] + 1},Append[l, Count[Table[GCD[l[[k]] + n, k], {k, n - 1}], 1]]];Nest[f, {1}, 74] (* _Ray Chandler_, Jan 22 2007 *)
%Y Cf. A127417.
%K nonn
%O 1,4
%A _Leroy Quet_, Jan 13 2007
%E Extended by _Ray Chandler_, Jan 22 2007
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