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

1,1

Comments

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

Links

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

Example

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

Mathematica

Select[Range[10^6], PrimeQ[#]&& PrimeQ[2#+1]&&!PrimeQ[2#+3]&]

Prog

(Magma) [p: p in PrimesUpTo(2500)| IsPrime(2*p+1) and not IsPrime(2*p+3)];
(PARI) is(n) = ispseudoprime(n) && ispseudoprime(2*n+1) && !ispseudoprime(2*n+3) \\ Felix Fröhlich, Jan 14 2017

Crossrefs

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

Sequence in context: A086497 A121509 A096071 * A342174 A159791 A078723

Adjacent sequences: A230114 A230115 A230116 * A230118 A230119 A230120

Keyword

nonn,easy

Author

Vincenzo Librandi, Oct 10 2013

Status

approved