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Numbers n such that 2*prime(n)+/-n are primes.
1

%I #6 Apr 07 2013 15:21:51

%S 1,3,15,27,33,45,81,189,213,243,249,279,285,291,381,423,567,615,675,

%T 687,705,813,819,1023,1071,1077,1137,1173,1347,1425,1431,1503,1737,

%U 1779,1785,1815,1857,1989,1995,2049,2067,2163,2241,2373,2565,2841

%N Numbers n such that 2*prime(n)+/-n are primes.

%H Harvey P. Dale, <a href="/A105549/b105549.txt">Table of n, a(n) for n = 1..1000</a>

%t bb={};Do[If[PrimeQ[2 Prime[n]+n]&&PrimeQ[2 Prime[n]-n], bb=Append[bb, n]], {n, 1, 3000, 2}];bb

%t Select[Range[3000],And@@PrimeQ[2Prime[#]+{#,-#}]&] (* _Harvey P. Dale_, Apr 07 2013 *)

%K nonn

%O 1,2

%A _Zak Seidov_, May 03 2005