OFFSET
1,2
EXAMPLE
a(1)=1 because 1*2 + 1 = 3 (a prime) and 1*6 + 1 = 7 (also a prime).
MATHEMATICA
Select[Range[400], PrimeQ[2#+1]&&PrimeQ[6#+1]&] (* Harvey P. Dale, Jan 17 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Mar 07 2010
EXTENSIONS
Corrected (118 removed, 132 replaced by 131) by R. J. Mathar, Apr 20 2010
Name edited by Jon E. Schoenfield, May 19 2019
STATUS
approved