A093139 Primes of the form 10*R_k + 7, where R_k is the repunit (A002275) of length k.

7, 17, 1117, 11117, 11111117, 11111111111111111111117, 11111111111111111111111111117, 1111111111111111111111111111111111111117

Offset

1,1

Comments

The next term has 131 digits. - Harvey P. Dale, Jul 05 2021

Links

Table of n, a(n) for n=1..8.

Makoto Kamada, Prime numbers of the form 11...117.

Index entries for primes involving repunits

Mathematica

Select[Table[FromDigits[PadLeft[{7}, n, 1]], {n, 50}], PrimeQ] (* Harvey P. Dale, Jul 05 2021 *)

Crossrefs

Cf. A056655 (corresponding k).

Sequence in context: A013540 A153375 A001145 * A177366 A138491 A022511

Adjacent sequences: A093136 A093137 A093138 * A093140 A093141 A093142

Keyword

nonn

Author

Rick L. Shepherd, Mar 23 2004

Status

approved