OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1001
EXAMPLE
181 becomes 1(9)8(9)1 which is prime 19891.
MATHEMATICA
Select[Range[10, 1000], PrimeQ[FromDigits[Riffle[IntegerDigits[#], 9]]]&] (* Harvey P. Dale, Oct 29 2014 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Aug 15 1999
EXTENSIONS
Offset changed to 1 by Georg Fischer, Oct 15 2019
STATUS
approved