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A115058 Primes p such that 3p+2 is not prime. 2


%S 2,11,31,41,47,53,61,67,71,73,101,107,109,113,131,137,151,157,179,181,

%T 191,193,211,223,229,241,251,263,271,277,281,283,307,311,331,347,359,

%U 373,379,389,401,421,431,443,449,461,463,467,487,491,509,521,541,547

%N Primes p such that 3p+2 is not prime.

%C Complement of A023208 in the prime numbers A000040.

%C Primes p that are also the largest prime factor of p(p^2-1)(3p+2)/24.

%D Number Theory, George E. Andrews 1971, Dover Publications New York, p 4.

%H Vincenzo Librandi, <a href="/A115058/b115058.txt">Table of n, a(n) for n = 1..1000</a>

%e p=11, p(p^2-1)(3p+2)/24 = 1925 = 5*5*7*11.

%t a={};Do[p=Prime[n];If[ !PrimeQ[3*p+2],AppendTo[a,p]],{n,8^2}];a - _Vladimir Joseph Stephan Orlovsky_, Apr 29 2008

%t Select[Prime[Range[100]], ! PrimeQ[3 # + 2]&] (* _Vincenzo Librandi_, Apr 17 2013 *)

%o (MAGMA) [p: p in PrimesUpTo(600) | not IsPrime(3*p + 2)]; // _Vincenzo Librandi_, Apr 17 2013

%K easy,nonn

%O 1,1

%A _Cino Hilliard_, Feb 28 2006

%E Edited by _Max Alekseyev_, Feb 06 2010

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Last modified December 16 01:43 EST 2019. Contains 330013 sequences. (Running on oeis4.)