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A163126 a(1)=1. a(n) = the number of integers k, 1 <= k <= n-1, where a(k) is coprime to n-k. 2

%I

%S 1,1,2,3,3,5,4,6,6,7,4,9,7,11,9,12,9,12,12,13,11,16,14,15,15,18,15,19,

%T 17,17,19,22,20,22,22,21,24,26,23,27,25,27,26,31,24,27,27,29,31,35,29,

%U 35,36,36,35,39,34,39,35,39,39,42,39,40,39,38,43,47,37,47,44,46,47,50,46,47,49,50,52,48,51,52,54,52,53,56,52,58,55,53,60,59,60,59,60,60,61,60,60,62

%N a(1)=1. a(n) = the number of integers k, 1 <= k <= n-1, where a(k) is coprime to n-k.

%H Vincenzo Librandi, <a href="/A163126/b163126.txt">Table of n, a(n) for n = 1..1000</a>

%t t={1}; Do[AppendTo[t, Length[Select[Range[n-1], CoprimeQ[t[[#]], n-#] &]]], {n, 2, 100}]; t

%Y A163127

%K nonn

%O 1,3

%A _Leroy Quet_, Jul 21 2009

%E More terms from _Sean A. Irvine_, Nov 29 2010

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Last modified June 25 16:08 EDT 2022. Contains 354851 sequences. (Running on oeis4.)