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a(n) = p, the lesser of twin primes (p, q=p+2) such that p*q + p + q is prime.
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%I #12 Jan 23 2015 16:09:54

%S 3,5,11,17,41,59,101,137,311,419,521,809,1019,1049,1151,1229,1319,

%T 1427,2111,2237,2267,3119,3329,3371,3539,4001,4049,4091,4217,4421,

%U 4721,5009,6359,6569,6689,6761,7487,7949,8537,8627,9629,9719,10007,10091,10709

%N a(n) = p, the lesser of twin primes (p, q=p+2) such that p*q + p + q is prime.

%C Or, primes p such that p+2 and 2 + 4*p + p^2 are prime.

%H Harvey P. Dale, <a href="/A128550/b128550.txt">Table of n, a(n) for n = 1..1000</a>

%e 3, 5 and 3*5+3+5=23 are prime; 5, 7 and 5*7+5+7=47 are prime; 11, 13 and 11*13+11+13 are primes.

%t lst={};Do[p=Prime[n];r=p+2;If[PrimeQ[r],If[PrimeQ[p*r+p+r],AppendTo[lst,p]]],{n,8!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Nov 28 2009 *)

%t Transpose[Select[Select[Partition[Prime[Range[1500]],2,1],#[[2]]- #[[1]] == 2&],PrimeQ[Times@@#+Total[#]]&]][[1]] (* _Harvey P. Dale_, Aug 24 2014 *)

%o (PARI) is(n)=isprime(n)&&isprime(n+2)&&isprime(n^2+4*n+2) \\ _Charles R Greathouse IV_, Jan 29 2013

%Y Cf. A096342, A126148, A128547, A128548, A128551.

%K nonn

%O 1,1

%A _Zak Seidov_, Mar 10 2007