

A230117


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


4



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
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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



