OFFSET
1,1
COMMENTS
EXAMPLE
a(5)=18289 so all the seven numbers 18289, 318289, 138289, 183289, 182389,
182839 & 182893 are primes.
MATHEMATICA
pp[n_, k_] := Catch[Block[{d = IntegerDigits@n}, Do[If[! PrimeQ[ FromDigits[ Insert[d, k, i]]], Throw[False]], {i, 1+Length@d}]; True]]; a[n_] := Catch[ Block[{p = NextPrime[10^(n-1)]}, While[p < 10^n, If[pp[p, 3], Throw@p, p = NextPrime@p]]; 0]]; a /@ Range[8] (* Giovanni Resta, Aug 13 2013 *)
CROSSREFS
KEYWORD
base,hard,more,nonn
AUTHOR
Farideh Firoozbakht, Sep 22 2009
EXTENSIONS
a(11)-a(13) from Donovan Johnson, Apr 14 2010
a(14) from Giovanni Resta, Aug 11 2013
STATUS
approved