OFFSET
1,1
COMMENTS
a(6k) = 0 as any 6k-digit number containing only digits 2 or 9 is divisible by 7. - Jinyuan Wang, Mar 09 2020
LINKS
Jinyuan Wang, Table of n, a(n) for n = 1..500
MATHEMATICA
Join[{2}, Table[Min[Select[FromDigits/@(Join[#, {9}]&/@Tuples[{2, 9}, n]), IntegerLength[#]==n+1&&PrimeQ[#]&]], {n, 20}]]/.\[Infinity]->0 (* Harvey P. Dale, Nov 08 2011 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Jan 04 1999
STATUS
approved