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 11-20 of 24 results. Next

A139071 Numbers k for which (10+k!)/10 is prime.

Original entry on oeis.org

5, 6, 11, 12, 15, 23, 26, 37, 45, 108, 112, 129, 137, 148, 172, 248, 760, 807, 975, 1398, 5231, 8765, 24182
Offset: 1

Views

Author

Artur Jasinski, Apr 07 2008

Keywords

Comments

Primes of the form (10+k!)/10 see A139070.
a(24) > 25000. - Robert Price, Nov 08 2016

Crossrefs

Programs

  • Mathematica
    a = {}; Do[If[PrimeQ[(n! + 10)/10], AppendTo[a, n]], {n, 1, 500}]; a
  • PARI
    for(k=5,1e3,if(ispseudoprime(k!/10+1),print1(k", "))) \\ Charles R Greathouse IV, Jul 15 2011

Extensions

More terms from Serge Batalov, Feb 18 2015
a(22)-a(23) from Robert Price, Nov 08 2016

A082671 Numbers n such that (n!-2)/2 is a prime.

Original entry on oeis.org

3, 4, 5, 6, 9, 31, 41, 373, 589, 812, 989, 1115, 1488, 1864, 1918, 4412, 4686, 5821, 13830
Offset: 1

Views

Author

Cino Hilliard, May 18 2003

Keywords

Examples

			(4!-2)/2 = 11 is a prime.
		

Crossrefs

Programs

  • Magma
    [n: n in [1..600]| IsPrime((Factorial(n)-2) div 2)]; // Vincenzo Librandi, Feb 18 2015
  • Mathematica
    Select[Range[0, 14000], PrimeQ[(#! - 2) / 2] &] (* Vincenzo Librandi, Feb 18 2015 *)
  • PARI
    xfactpk(n,k=2) = { for(x=2,n, y = (x!-k)/k; if(isprime(y),print1(x", ")) ) }
    

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
Edited by T. D. Noe, Oct 30 2008

A139199 Numbers k such that (k!-4)/4 is prime.

Original entry on oeis.org

4, 5, 6, 7, 8, 10, 15, 18, 23, 157, 165, 183, 184, 362, 611, 908, 2940, 6875, 9446, 16041
Offset: 1

Views

Author

Artur Jasinski, Apr 11 2008

Keywords

Comments

Numbers k such that (k!-m)/m is prime:
for m=1 see A002982
for m=2 prime or pseudoprime see A082671
for m=3 see A139056
for m=4 see A139199
for m=5 see A139200
for m=6 see A139201
for m=7 see A139202
for m=8 see A139203
for m=9 see A139204
for m=10 see A139205
a(17) > 2000 - Ray G. Opao, Sep 30 2008
a(21) > 25000 - Robert Price, Sep 25 2016

Crossrefs

Programs

  • Mathematica
    a = {}; Do[If[PrimeQ[(n! - 4)/4], Print[a]; AppendTo[a, n]], {n, 1, 184}]; a (*Artur Jasinski*)
  • PARI
    is(n)=n>3 && isprime(n!/4-1) \\ Charles R Greathouse IV, Apr 29 2015

Extensions

a(15)-a(16) from Ray G. Opao, Sep 30 2008
a(17) from Serge Batalov, Feb 18 2015
a(18)-a(20) from Robert Price, Sep 25 2016

A139205 Numbers k such that (k!-10)/10 is prime.

Original entry on oeis.org

5, 6, 7, 11, 13, 17, 28, 81, 87, 433, 640, 647, 798, 1026, 1216, 1277, 3825, 6684
Offset: 1

Views

Author

Artur Jasinski, Apr 11 2008

Keywords

Comments

a(19) > 25000. - Robert Price, Dec 23 2016

Crossrefs

Programs

  • Mathematica
    a = {}; Do[If[PrimeQ[(n! - 10)/10], Print[a]; AppendTo[a, n]], {n, 1, 300}]; a (*Artur Jasinski*)
    Select[Range[700],PrimeQ[(#!-10)/10]&] (* Harvey P. Dale, Feb 15 2015 *)

Extensions

One additional term (a(12)) from Harvey P. Dale, Feb 15 2015
More terms from Serge Batalov, Feb 18 2015
a(18) from Robert Price, Dec 23 2016

A151913 Numbers n for which (8+n!)/8 is prime.

Original entry on oeis.org

7, 9, 10, 12, 14, 20, 23, 24, 29, 44, 108, 2049, 3072, 4862, 8807, 15089
Offset: 1

Views

Author

Artur Jasinski, Apr 07 2008

Keywords

Comments

a(17) > 25000. - Robert Price, Dec 20 2016

Crossrefs

For primes of the form (8+k!!)/8 see A139066.
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! + 8)/8], AppendTo[a, n]], {n, 1, 500}]; a
  • PARI
    is(n)=n>6 && isprime((8+n!)/8) \\ Charles R Greathouse IV, Apr 29 2016

Extensions

Definition corrected Feb 24 2010
More terms from Serge Batalov, Feb 18 2015
a(15)-a(16) from Robert Price, Dec 20 2016

A076680 Numbers k such that 4*k! + 1 is prime.

Original entry on oeis.org

0, 1, 4, 7, 8, 9, 13, 16, 28, 54, 86, 129, 190, 351, 466, 697, 938, 1510, 2748, 2878, 3396, 4057, 4384, 5534, 7069, 10364
Offset: 1

Views

Author

Phillip L. Poplin (plpoplin(AT)bellsouth.net), Oct 25 2002

Keywords

Comments

a(25) > 6311. - Jinyuan Wang, Feb 06 2020

Examples

			k = 7 is a term because 4*7! + 1 = 20161 is prime.
		

Crossrefs

Cf. m*n!-1 is a prime: A076133, A076134, A099350, A099351, A180627-A180631.
Cf. m*n!+1 is a prime: A051915, A076679-A076683, A178488, A180626, A126896.
Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205.

Programs

  • Mathematica
    Select[Range[5000],PrimeQ[4#!+1]&] (* Harvey P. Dale, Mar 23 2011 *)
  • PARI
    is(k) = ispseudoprime(4*k!+1); \\ Jinyuan Wang, Feb 06 2020

Extensions

Corrected (added missed terms 2748, 2878) by Serge Batalov, Feb 24 2015
a(24) from Jinyuan Wang, Feb 06 2020
a(25)-a(26) from Michael S. Branicky, Jul 04 2024

A139060 Primes of the form (4+k!)/4.

Original entry on oeis.org

7, 31, 181, 1556755201, 12772735542927360001, 3877802510832746496000001, 65782709233423382541804503040000001, 203978820811974433586402817399028973568000000001
Offset: 1

Views

Author

Artur Jasinski, Apr 07 2008

Keywords

Comments

For numbers k for which (4+k!)/4 is prime see A139061.

Crossrefs

Programs

  • Mathematica
    a = {}; Do[If[PrimeQ[(n! + 4)/4], AppendTo[a, (n! + 4)/4]], {n, 1, 50}]; a
    Select[(4+Range[100]!)/4,PrimeQ] (* Harvey P. Dale, Oct 05 2016 *)
  • PARI
    for(k=4,1e3,if(ispseudoprime(t=k!/4+1),print1(t", "))) \\ Charles R Greathouse IV, Jul 15 2011

Formula

a(n) = A139151(A139061(n)). - Amiram Eldar, Oct 13 2024

A139062 Primes of the form (6+k!)/6.

Original entry on oeis.org

2, 5, 604801, 6652801, 1037836801, 14529715201, 59281238016001, 8515157028618240001
Offset: 1

Views

Author

Artur Jasinski, Apr 07 2008

Keywords

Comments

For numbers k for which (6+k!)/6 is prime see A139063.

Crossrefs

Programs

  • Mathematica
    a = {}; Do[If[PrimeQ[(n! + 6)/6], AppendTo[a, (n! + 6)/6]], {n, 1, 50}]; a
  • PARI
    for(k=3,1e3,if(ispseudoprime(t=k!/6+1),print1(t", "))) \\ Charles R Greathouse IV, Jul 15 2011

Formula

a(n) = A139153(A139063(n)). - Amiram Eldar, Oct 14 2024

A139064 Primes of the form (7+k!)/7.

Original entry on oeis.org

5702401, 186810624001, 2988969984001, 2215887149047283712000001, 1476163995198020704238093048217600000001, 19811874077955690819705574245769915192271839538955347505831613562880000000000001
Offset: 1

Views

Author

Artur Jasinski, Apr 07 2008

Keywords

Comments

For numbers k for which (7+k!)/7 is prime see A139065.

Crossrefs

Programs

  • Mathematica
    a = {}; Do[If[PrimeQ[(n! + 7)/7], AppendTo[a, (n! + 7)/7]], {n, 1, 50}]; a
  • PARI
    for(k=7,1e3,if(ispseudoprime(t=k!/7+1),print1(t", "))) \\ Charles R Greathouse IV, Jul 15 2011

Formula

a(n) = A139154(A139065(n)). - Amiram Eldar, Oct 14 2024

A139200 Numbers k such that (k!-5)/5 is prime.

Original entry on oeis.org

5, 11, 12, 16, 36, 41, 42, 47, 127, 136, 356, 829, 1863, 2065, 2702, 4509, 7498
Offset: 1

Views

Author

Artur Jasinski, Apr 11 2008

Keywords

Comments

a(16) > 3000. - Ray G. Opao, Oct 05 2008
a(18) > 25000. - Robert Price, Nov 20 2016

Crossrefs

Programs

  • Magma
    [n: n in [5..500] | IsPrime((Factorial(n)-5) div 5)]; // Vincenzo Librandi, Nov 21 2016
  • Mathematica
    a = {}; Do[If[PrimeQ[(n! - 5)/5], Print[a]; AppendTo[a, n]], {n, 1, 300}]; a (* Artur Jasinski *)

Extensions

a(13)-a(15) from Ray G. Opao, Oct 05 2008
a(16) from Serge Batalov, Feb 18 2015
a(17) from Robert Price, Nov 20 2016
Previous Showing 11-20 of 24 results. Next