A093944 Primes of the form 9*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

97, 977, 97777, 97777777777777777777, 97777777777777777777777777777, 97777777777777777777777777777777777777777777777777777777777777777777777777

Offset

1,1

Comments

The next term has 204 digits. - Harvey P. Dale, May 22 2014

Links

Table of n, a(n) for n=1..6.

Makoto Kamada, Prime numbers of the form 977...77.

Index entries for primes involving repunits

Mathematica

Select[Table[FromDigits[PadRight[{9}, n, 7]], {n, 250}], PrimeQ] (* Harvey P. Dale, May 22 2014 *)

Crossrefs

Cf. A002275, A056727 (corresponding k).

Sequence in context: A262925 A093297 A068852 * A127748 A127828 A186075

Adjacent sequences: A093941 A093942 A093943 * A093945 A093946 A093947

Keyword

nonn

Author

Rick L. Shepherd, Apr 17 2004

Status

approved