cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A093946 Primes of the form 6*10^k - 1.

Original entry on oeis.org

5, 59, 599, 59999, 599999, 59999999, 59999999999, 59999999999999, 59999999999999999999999, 599999999999999999999999, 59999999999999999999999999999, 59999999999999999999999999999999999
Offset: 1

Views

Author

Rick L. Shepherd, Apr 17 2004

Keywords

Comments

Equivalently, primes of the form 5*10^n + 9*R_n, where R_n is the repunit (A002275) of length n.

Links

Crossrefs

Cf. A002275, A056716.
Primes in A099151.

Programs

  • Magma
    [a: n in [0..200] | IsPrime(a) where a is (6*10^n-1)]; // Vincenzo Librandi, May 08 2019
  • Mathematica
    Select[Table[FromDigits[PadRight[{5},n,9]],{n,40}],PrimeQ] (* Harvey P. Dale, Jun 06 2016 *)

Formula

a(n) = 6*10^A056716(n) - 1 = A099151(A056716(n) + 1). - Elmo R. Oliveira, Jun 14 2025
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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