OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
MATHEMATICA
Select[Range[4, 3000], PrimeQ[#]&& ! PrimeQ[2 # - 5] &](* Vincenzo Librandi, Sep 15 2013 *)
Select[Prime[Range[100]], CompositeQ[2#-5]&] (* Harvey P. Dale, May 16 2016 *)
PROG
(Magma) [p: p in PrimesInInterval(4, 600)| not IsPrime(2*p-5)]; // Vincenzo Librandi, Sep 15 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 04 2009
EXTENSIONS
Corrected (229 inserted) by R. J. Mathar, Nov 30 2009
Corrected (3 deleted, as 2*3-5 = 1 and 1 is not composite) by Harvey P. Dale, May 16 2016
STATUS
approved