A092675 Primes of the form 80*R_k + 1, where R_k is the repunit (A002275) of length k.

881, 8888888888888888881, 8888888888888888888888888888888888888888888888888888888888888888888888888888881

Offset: 1

Author

Rick L. Shepherd, Mar 02 2004

Keywords

• bref
• nonn

Comments

Primes of the form 888...881.

The number of 8's in each term is given by the corresponding term of A056664 and so the first term too large to include above is 888...8881 (with 138 8's).

Primes of the form (8*10^k - 71)/9. - Vincenzo Librandi, Nov 16 2010

Links

• Makoto Kamada, Prime numbers of the form 88...881.
• Index entries for primes involving repunits

Crossrefs

Cf. A056664 (corresponding k).

Cf. A051200, A004022, A093176, A093177, A089346, A093174, A092571.

Programs

Mathematica

Select[Table[10 FromDigits[PadRight[{},n,8]]+1,{n,150}],PrimeQ] (* Harvey P. Dale, Aug 07 2019 *)