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.

Previous Showing 21-24 of 24 results.

A139201 Numbers k such that (k!-6)/6 is prime.

Original entry on oeis.org

4, 5, 7, 8, 11, 14, 16, 17, 18, 20, 43, 50, 55, 59, 171, 461, 859, 2830, 3818, 5421, 5593, 10118, 10880, 24350
Offset: 1

Views

Author

Artur Jasinski, Apr 11 2008

Keywords

Comments

a(25) > 25000. - Robert Price, Dec 15 2016

Crossrefs

Cf. A139189, A139190, A139191, A139192, A139193, A139194, A139195, A139196, A139197, A139198.
Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205; n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071 (1 <= m <= 10).

Programs

  • Maple
    a:=proc(n) if isprime((1/6)*factorial(n)-1)=true then n else end if end proc: seq(a(n),n=4..500); # Emeric Deutsch, Apr 29 2008
  • Mathematica
    a = {}; Do[If[PrimeQ[(n! - 6)/6], Print[a]; AppendTo[a, n]], {n, 1, 300}]; a (* Artur Jasinski *)

Extensions

2 more terms from Emeric Deutsch, Apr 29 2008
More terms from Serge Batalov, Feb 18 2015
a(22)-a(24) from Robert Price, Dec 15 2016

A139202 Numbers k such that (k!-7)/7 is prime.

Original entry on oeis.org

7, 9, 20, 23, 46, 54, 57, 71, 85, 387, 396, 606, 1121, 2484, 6786, 9321, 11881, 18372
Offset: 1

Views

Author

Artur Jasinski, Apr 11 2008

Keywords

Comments

a(19) > 25000. - Robert Price, Nov 05 2016

Crossrefs

Cf. A139189, A139190, A139191, A139192, A139193, A139194, A139195, A139196, A139197, A139198.
Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205; n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071 (1<=m<=10).

Programs

  • Mathematica
    a = {}; Do[If[PrimeQ[(n! - 7)/7], Print[a]; AppendTo[a, n]], {n, 1, 300}]; a (*Artur Jasinski*)

Extensions

More terms from Alexis Olson (AlexisOlson(AT)gmail.com), Nov 14 2008
a(13)-a(14) PRPs from Sean A. Irvine, Aug 05 2010
a(15)-a(18) PRP from Robert Price, Nov 05 2016

A139203 Numbers k such that (k!-8)/8 is prime.

Original entry on oeis.org

4, 6, 8, 10, 11, 16, 19, 47, 66, 183, 376, 507, 1081, 1204, 12111, 23181
Offset: 1

Views

Author

Artur Jasinski, Apr 11 2008

Keywords

Comments

a(17) > 25000. - Robert Price, Oct 08 2016

Crossrefs

Cf. A139189, A139190, A139191, A139192, A139193, A139194, A139195, A139196, A139197, A139198.
Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205; n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071 (1<=m<=10).

Programs

  • Maple
    a:=proc(n) if isprime((1/8)*factorial(n)-1)=true then n else end if end proc: seq(a(n),n=4..550); # Emeric Deutsch, May 07 2008
  • Mathematica
    a = {}; Do[If[PrimeQ[(n! - 8)/8], Print[a]; AppendTo[a, n]], {n, 1, 300}]; a

Extensions

2 more terms from Emeric Deutsch, May 07 2008
More terms from Serge Batalov, Feb 18 2015
a(15)-a(16) from Robert Price, Oct 08 2016

A139204 Numbers k such that (k!-9)/9 is prime.

Original entry on oeis.org

6, 15, 17, 18, 21, 27, 29, 30, 37, 47, 50, 64, 125, 251, 602, 611, 1184, 1468, 5570, 10679, 15798, 21237
Offset: 1

Views

Author

Artur Jasinski, Apr 11 2008

Keywords

Comments

a(20) > 10000. The PFGW program has been used to certify all the terms up to a(19), using a deterministic test which exploits the factorization of a(n) + 1. - Giovanni Resta, Mar 28 2014
a(23) > 25000. - Robert Price, Mar 29 2017

Crossrefs

Cf. A139189, A139190, A139191, A139192, A139193, A139194, A139195, A139196, A139197, A139198.
Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205; n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071 (1<=m<=10).

Programs

  • Mathematica
    a = {}; Do[If[PrimeQ[(n! - 9)/9], Print[a]; AppendTo[a, n]], {n, 1, 300}]; a
  • PARI
    for(n=1,1000,if(floor(n!/9-1)==n!/9-1,if(ispseudoprime(n!/9-1),print(n)))) \\ Derek Orr, Mar 28 2014

Extensions

a(14)-a(16) from Derek Orr, Mar 28 2014
a(17)-a(19) from Giovanni Resta, Mar 28 2014
a(20)-a(22) from Robert Price, Mar 29 2017
Previous Showing 21-24 of 24 results.

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