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.

A217380 Numbers k such that 8^k - 7 is prime.

Original entry on oeis.org

13, 661, 773, 833, 4273, 40613, 302913
Offset: 1

Views

Author

Vincenzo Librandi, Oct 02 2012

Keywords

Comments

All terms are equal to 1/3 of the multiples of 3 in A059609.
Naturally these numbers are odd since (9-1)^(2n)-7 is divisible by 3. - Bruno Berselli, Oct 04 2012

Crossrefs

Cf. A059609, A217353, A217356.

Programs

  • Mathematica
    Select[Range[4000], PrimeQ[8^# - 7] &]
  • PARI
    is(n)=ispseudoprime(8^n-7) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(7) using A059609 from Michael S. Branicky, Sep 15 2024

A217383 Numbers k such that 8^k - 9 is prime.

Original entry on oeis.org

3, 7, 11, 47, 81, 95, 107, 179, 233, 243, 947, 2817, 2859, 3233, 7563, 11307, 218615, 225587, 1160027
Offset: 1

Views

Author

Vincenzo Librandi, Oct 03 2012

Keywords

Comments

All terms are equal to 1/3 of the multiples of 3 in A059610.
Naturally these numbers are odd since 8^(2n)-9 = (8^n-3)(8^n+3) is composite. - Bruno Berselli, Oct 04 2012

Crossrefs

Cf. A059610, A217356, A217382.

Programs

  • Mathematica
    Select[Range[10000], PrimeQ[8^# - 9] &]
  • PARI
    is(n)=ispseudoprime(8^n-9) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(17)-a(18) using A059610 from Michael S. Branicky, Jul 14 2023
a(19) using A059610 from Michael S. Branicky, Apr 23 2025
Showing 1-2 of 2 results.

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

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