A093404 Primes of the form 70*R_k + 9, where R_k is the repunit (A002275) of length k.

79, 777777777777777777777777777777777777777777777777777777777777777779, 77777777777777777777777777777777777777777777777777777777777777777777777777777777777779, 777777777777777777777777777777777777777777777777777777777777777777777777777777777777777779

Offset

1,1

Comments

Primes of the form (7*10^k + 11)/9. - Vincenzo Librandi, Nov 16 2010

Links

Table of n, a(n) for n=1..4.

Makoto Kamada, Prime numbers of the form 77...779.

Index entries for primes involving repunits

Mathematica

Select[Table[FromDigits[PadLeft[{9}, n, 7]], {n, 100}], PrimeQ] (* Harvey P. Dale, May 09 2012 *)

Crossrefs

Cf. A002275, A056693 (corresponding k), A098089.

Sequence in context: A060711 A128472 A243432 * A236236 A031136 A050456

Adjacent sequences: A093401 A093402 A093403 * A093405 A093406 A093407

Keyword

nonn

Author

Rick L. Shepherd, Mar 28 2004

Status

approved