OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
41 is a member as 41941 and 9419 are both prime.
MATHEMATICA
n9Q[n_]:=Module[{idn=IntegerDigits[n]}, AllTrue[{FromDigits[Join[idn, {9}, idn]], FromDigits[ Join[{9}, idn, {9}]]}, PrimeQ]]; Select[Range[2500], n9Q] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Feb 01 2016 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Nov 28 2003
EXTENSIONS
More terms from mohammed bouayoun (bouyao(AT)wanadoo.fr), Feb 02 2004
STATUS
approved