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

2, 11, 31, 41, 47, 53, 61, 67, 71, 73, 101, 107, 109, 113, 131, 137, 151, 157, 179, 181, 191, 193, 211, 223, 229, 241, 251, 263, 271, 277, 281, 283, 307, 311, 331, 347, 359, 373, 379, 389, 401, 421, 431, 443, 449, 461, 463, 467, 487, 491, 509, 521, 541, 547

Offset: 1

Author

Cino Hilliard, Feb 28 2006

Keywords

• easy
• nonn

Comments

Complement of A023208 in the prime numbers A000040.

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

Examples

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

References

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

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Programs

Magma

[p: p in PrimesUpTo(600) | not IsPrime(3*p + 2)]; // Vincenzo Librandi, Apr 17 2013

Mathematica

a={};Do[p=Prime[n];If[ !PrimeQ[3*p+2],AppendTo[a,p]],{n,101}];a (* Vladimir Joseph Stephan Orlovsky, Apr 29 2008 *)
Select[Prime[Range[100]], ! PrimeQ[3 # + 2]&] (* Vincenzo Librandi, Apr 17 2013 *)

Extensions

Edited by Max Alekseyev, Feb 06 2010