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.

Showing 1-2 of 2 results.

A093168 Primes of the form 30*R_k + 7, where R_k is the repunit (A002275) of length k.

Original entry on oeis.org

7, 37, 337, 333337, 3333333333333333333333333333333333333333333337
Offset: 1

Views

Author

Rick L. Shepherd, Mar 26 2004

Keywords

Comments

Primes of the form (3*10^k + 33)/9. - Vincenzo Librandi, Nov 16 2010

Links

Crossrefs

Cf. A056680 (corresponding k), A099411, A173766.

A099411 Numbers k such that 3*R_k + 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

Original entry on oeis.org

1, 2, 3, 6, 46, 394, 978, 2586, 2811, 2968, 3642, 4827, 4918, 5592, 5706, 10683, 12891, 14118, 74350, 88680, 162138, 279978
Offset: 1

Views

Author

Robert G. Wilson v, Oct 14 2004

Keywords

Comments

Also numbers k such that (10^k + 11)/3 is prime.
a(21) > 10^5. - Robert Price, Nov 02 2014

Links

Crossrefs

Cf. A002275, A056680, A093168.

Programs

  • Mathematica
    Do[ If[ PrimeQ[ 3(10^n - 1)/9 + 4], Print[n]], {n, 10000}]

Formula

a(n) = A056680(n) + 1.

Extensions

a(16)-a(20) from Robert Price, Nov 02 2014
a(21)-a(22) from Kamada data by Tyler Busby, May 03 2024
Showing 1-2 of 2 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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