A093942 Primes of the form 6*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

67, 677, 67777, 67777777777, 67777777777777, 67777777777777777777777777, 67777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777

Offset

1,1

Comments

The next term is too large to display (see A056718).

The next term has 180 digits. - Harvey P. Dale, Jun 15 2021

Links

Table of n, a(n) for n=1..7.

Makoto Kamada, Prime numbers of the form 677...77.

Index entries for primes involving repunits.

Mathematica

Select[Table[FromDigits[PadRight[{6}, n, 7]], {n, 120}], PrimeQ] (* Harvey P. Dale, Jun 15 2021 *)

Crossrefs

Cf. A056718 (corresponding k).

Sequence in context: A142139 A178004 A106106 * A166802 A212557 A254640

Adjacent sequences: A093939 A093940 A093941 * A093943 A093944 A093945

Keyword

nonn

Author

Rick L. Shepherd, Apr 17 2004

Status

approved