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A154670 Averages of twin prime pairs n such that n*2 and n/2 are squares. 8

%I

%S 18,72,882,1152,2592,3528,4050,15138,20808,34848,46818,69192,83232,

%T 103968,112338,149058,176418,180000,206082,281250,362952,388962,

%U 438048,472392,478242,538722,649800,734472,808992,960498,1080450,1143072

%N Averages of twin prime pairs n such that n*2 and n/2 are squares.

%C 18/2=9=3^2, 18*2=26=6^2,...

%F a(n) = 18*A037073(n)^2 - _M. F. Hasler_, Jan 15 2009

%t lst={};Do[If[PrimeQ[n-1]&&PrimeQ[n+1],s=Sqrt[n*2];If[Floor[s]==s,AppendTo[lst,n]]],{n,6,10!,6}];lst...and/or... lst={};Do[If[PrimeQ[n-1]&&PrimeQ[n+1],s=Sqrt[n/2];If[Floor[s]==s,AppendTo[lst,n]]],{n,6,10!,6}];lst

%o (PARI) for(i=1,999, isprime(18*i^2+1) && isprime(18*i^2-1) && print1(18*i^2",")) \\ _M. F. Hasler_, Jan 15 2009

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Jan 13 2009

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Last modified October 20 15:14 EDT 2017. Contains 293612 sequences.