OFFSET
1,2
EXAMPLE
a(3) = 5; 10*5^2+1 = 251. 251+6 = 257; 251+12 = 263; 251+18=269. 251, 257, 263 and 269 are all primes.
MATHEMATICA
pQ[n_]:=Module[{x=10n^2+1}, And@@PrimeQ/@(x+ {0, 6, 12, 18})]; Select[Range[12000], pQ] (* Harvey P. Dale, Mar 22 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ray G. Opao, Mar 24 2004
EXTENSIONS
More terms from Harvey P. Dale, Mar 22 2011.
STATUS
approved