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A161888 a(n) = the smallest positive integer that does not divide n, and is such that sum{k=1 to n} a(k) is coprime to n. 2

%I

%S 2,3,2,6,3,7,2,6,4,4,2,8,2,4,4,6,2,4,2,6,4,4,2,14,3,3,4,8,2,4,2,6,2,4,

%T 2,8,2,4,4,6,2,4,2,6,6,4,2,10,2,4,2,6,2,4,3,3,4,4,2,8,2,4,4,6,3,5,2,6,

%U 2,8,2,10,2,4,4,6,3,9,2,6,4,4,2,8,3,3,4,6,2,4,2,6,4,4,3,5,2,4,2,8,2,8,2,6,2

%N a(n) = the smallest positive integer that does not divide n, and is such that sum{k=1 to n} a(k) is coprime to n.

%C Sum{k=1 to n} a(k) = A161889(n).

%H Harvey P. Dale, <a href="/A161888/b161888.txt">Table of n, a(n) for n = 1..1000</a>

%t spi[{n_,s_,a_}]:=Module[{k=1},While[Divisible[n+1,k]||!CoprimeQ[s+k, n+1], k++];{n+1,s+k,k}]; Transpose[NestList[spi,{1,2,2},105]][[3]] (* _Harvey P. Dale_, May 26 2015 *)

%Y Cf. A161889

%K nonn

%O 1,1

%A _Leroy Quet_, Jun 21 2009

%E More terms from _Sean A. Irvine_, Aug 10 2010

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Last modified September 21 11:09 EDT 2021. Contains 347597 sequences. (Running on oeis4.)