A230225 Primes p such that 2*p+1 and 2*p+3 are not prime.

31, 37, 59, 61, 71, 79, 101, 103, 107, 109, 149, 151, 163, 181, 211, 241, 257, 263, 271, 311, 313, 317, 331, 347, 367, 373, 389, 401, 421, 433, 449, 457, 461, 479, 499, 521, 541, 569, 571, 577, 587, 601, 619, 631, 661, 673, 677, 691, 701, 709, 727, 733, 751

Offset: 1

Author

Vincenzo Librandi, Oct 12 2013

Keywords

• nonn
• easy

Examples

			31 is in the sequence because 2*31+1=63 and 2*31+3=65 are not prime.
		

Links

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

Crossrefs

Cf. A005384, A023204, A053176, A089531, A126107, A163769, A230039, A230117.

Programs

Magma

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

Mathematica

Select[Range[10^3], PrimeQ[#]&&!PrimeQ[2 # + 1]&&!PrimeQ[2 # + 3]&]
Select[Prime[Range[200]],NoneTrue[2#+{1,3},PrimeQ]&] (* Harvey P. Dale, Sep 19 2021 *)