login
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
OFFSET
1,1
COMMENTS
Intersection of A005384 and A163769. - Felix Fröhlich, Jan 14 2017
LINKS
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
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Oct 10 2013
STATUS
approved