OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
a(1)=1 because 2*1-1=1 is nonprime and 2*1+1=3 is prime.
MATHEMATICA
Select[Range[1, 341, 2], !PrimeQ[#]&&Total[Boole[PrimeQ[2 #+{1, -1}]]]==1&] (* Harvey P. Dale, Sep 01 2017 *)
CROSSREFS
KEYWORD
nonn,easy,less
AUTHOR
Juri-Stepan Gerasimov, Feb 10 2010
EXTENSIONS
Corrected at 3 or more places by R. J. Mathar, Mar 09 2010
STATUS
approved