A093938 Primes of the form 2*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

2, 277, 2777, 2777777777, 2777777777777777, 2777777777777777777, 2777777777777777777777777777777777777, 2777777777777777777777777777777777777777777777777777777777777777

Offset: 1

Author

Rick L. Shepherd, Apr 17 2004

Keywords

• nonn

Links

• Makoto Kamada, Prime numbers of the form 277...77.
• Index entries for primes involving repunits

Crossrefs

Cf. A002275, A056702 (corresponding k).

Programs

Mathematica

Select[FromDigits/@Table[PadRight[{2},n,7],{n,200}], PrimeQ] (* Harvey P. Dale, May 14 2011 *)