A036939 Smallest n-digit prime containing only digits 2 and 9, or 0 if no such prime exists.

2, 29, 229, 2999, 22229, 0, 2222929, 22229299, 222229229, 2222229299, 22222229299, 0, 2222222229229, 22222222222229, 222222222229229, 2222222222229299, 22222222222922299, 0, 2222222222222292929

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

Cf. A020460, A036229, A036313.

Sequence in context: A261268 A020460 A178000 * A342962 A342971 A124301

Adjacent sequences: A036936 A036937 A036938 * A036940 A036941 A036942

Keyword

nonn,base

Author

Patrick De Geest, Jan 04 1999

Status

approved