A230117 Primes p such that 2*p+1 is prime and 2*p+3 is not prime.

3, 11, 23, 41, 83, 131, 179, 191, 233, 239, 251, 281, 293, 359, 419, 431, 443, 491, 593, 641, 653, 683, 719, 761, 911, 953, 1019, 1031, 1049, 1103, 1223, 1229, 1289, 1409, 1439, 1451, 1481, 1511, 1601, 1811, 1889, 1901, 1931, 1973, 2003, 2039, 2069, 2141

Offset: 1

Author

Vincenzo Librandi, Oct 10 2013

Keywords

• nonn
• easy

Comments

Intersection of A005384 and A163769. - Felix Fröhlich, Jan 14 2017

Examples

			23 is in the sequence because 2*23+1=47 (prime) and 2*23+3=49 (not prime).
		

Links

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

Crossrefs

Cf. A005384, A023204, A053176, A126107, A163769, A230039.

Programs

Magma

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

Mathematica

Select[Range[10^6],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