OFFSET
1,1
COMMENTS
This is A130699 with the trivial multiples of 3 removed.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..2500
EXAMPLE
26 because 2*26+3=55 is not a prime, nor is 2*26-3=49.
MATHEMATICA
Select[Range[400], !Divisible[#, 3]&&NoneTrue[2#+{3, -3}, PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 19 2018 *)
PROG
(PARI) isok(n) = (n % 3) && !isprime(2*n-3) && !isprime(2*n+3) \\ Michel Marcus, Jul 11 2013
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
W. Neville Holmes, Jul 14 2007
EXTENSIONS
Missing term 169 added by Michel Marcus, Jul 11 2013
STATUS
approved