A230039 Primes p such that 2*p+1 is not prime and 2*p+3 is prime.

7, 13, 17, 19, 43, 47, 67, 73, 97, 127, 137, 139, 157, 167, 193, 197, 199, 223, 227, 229, 269, 277, 283, 307, 337, 349, 353, 379, 383, 397, 409, 439, 463, 467, 487, 503, 523, 547, 557, 563, 599, 607, 613, 617, 643, 647, 739, 773, 797, 827, 853, 859, 887, 929

Offset: 1

Author

Vincenzo Librandi, Oct 10 2013

Keywords

• nonn
• easy

Comments

Intersection of A023204 and A053176. - Felix Fröhlich, Jan 14 2017

Examples

			43 is in the sequence because 2*43+1=87 (not prime) and 2*43+3=89 (prime).
		

Links

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

Crossrefs

Cf. A005384, A023204, A053176, A126107, A163769, A230117.

Programs

Magma

[p: p in PrimesUpTo(2500)|not IsPrime(2*p+1) and IsPrime(2*p+3)];

Mathematica

Select[Range[10^5],PrimeQ[#]&& !PrimeQ[2#+1]&& PrimeQ[2#+3]&]

PARI

is(n) = ispseudoprime(n) && !ispseudoprime(2*n+1) && ispseudoprime(2*n+3) \\ Felix Fröhlich, Jan 14 2017