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A214586 Numbers k such that gcd(k!!+1,k-1) = 1. 3

%I

%S 2,6,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,50,52,

%T 54,56,58,62,64,66,68,70,72,74,76,78,82,86,88,90,92,94,96,98,100,102,

%U 106,110,112,114,116,118,120,122,124,126

%N Numbers k such that gcd(k!!+1,k-1) = 1.

%C Positions of 2 in A214054; complement of A214585.

%H Clark Kimberling, <a href="/A214586/b214586.txt">Table of n, a(n) for n = 1..1000</a>

%t b[n_]:=n!!;c[n_]:=n;

%t t=Table[m=1;While[GCD[b[n]+m,c[n]-m]==1,m++];m,{n,1,200}] (* A214054 *)

%t Flatten[Position[t,1]] (* A214585 *)

%t Flatten[Position[t,2]] (* A214586 *)

%t Select[Range[150],CoprimeQ[#!!+1,#-1]&] (* _Harvey P. Dale_, Dec 13 2014 *)

%Y Cf. A214054, A214585.

%K nonn

%O 1,1

%A _Clark Kimberling_, Jul 21 2012

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Last modified September 23 04:54 EDT 2020. Contains 337295 sequences. (Running on oeis4.)