OFFSET
1,1
COMMENTS
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
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Oct 10 2013
STATUS
approved