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 1-7 of 7 results.

A262772 Numbers k such that k!! - 32 is prime.

Original entry on oeis.org

7, 45, 67, 145, 411, 825, 1021, 4039, 9069, 9789, 12463, 15137, 26313, 27499
Offset: 1

Views

Author

Robert Price, Sep 30 2015

Keywords

Comments

Corresponding primes are 73, 25373791335626257947657609343, ... .
a(15) > 50000.

Links

Crossrefs

Cf. A006882, A007749, A094144, A123910, A258616.

Programs

  • Magma
    DoubleFactorial:=func< n | &*[n..2 by -2] >; [ n: n in [7..450] | IsPrime(DoubleFactorial(n) -32) ]; // Vincenzo Librandi, Oct 01 2015
  • Mathematica
    Select[Range[0, 50000], If[#!! - 32 > 0, PrimeQ[#!! - 32]] &]
  • PARI
    for(n=1, 1e4, if (isprime(prod(k=0, (n-1)\2, n - 2*k ) - 32),print1(n", "))) \\ Altug Alkan, Oct 01 2015

A258452 Numbers n such that n!! - 512 is prime.

Original entry on oeis.org

9, 11, 21, 23, 45, 65, 79, 153, 155, 199, 361, 799, 883, 1237, 1253, 1753, 4975, 5117, 5843, 8179, 12831
Offset: 1

Views

Author

Robert Price, Nov 05 2015

Keywords

Comments

Corresponding primes are 433, 9883, 13749310063, 316234142713, ... .
a(22) > 50000.

Links

Crossrefs

Cf. A006882, A007749, A094144, A123910, A258616, A262772.

Programs

  • Mathematica
    Select[Range[0, 50000], If[#!! - 512 > 0, PrimeQ[#!! - 512]] &]
  • PARI
    for(n=1, 1e4, if (ispseudoprime(m=prod(k=0, (n-1)\2, n - 2*k) - 512), print1(n", "))) \\ Altug Alkan, Nov 06 2015

A265201 Numbers n such that n!!! - 3^10 is prime, where n!3 = n!!! is a triple factorial number (A007661).

Original entry on oeis.org

19, 20, 22, 26, 41, 55, 56, 152, 155, 316, 347, 383, 500, 556, 646, 656, 748, 976, 1433, 2213, 2680, 2911, 3373, 4799, 4964, 7189, 8798, 9871, 14069, 14627, 16657, 20230, 24137, 24430, 28331, 36313, 41522, 43031, 46072, 47719
Offset: 1

Views

Author

Robert Price, Dec 04 2015

Keywords

Comments

Corresponding primes are 1047511, 4129751, 24285271, 2504843351, 126757680265156951, ... .
a(41) > 50000.

Examples

			19!3 - 3^10 = 19*16*13*10*7*4*1 - 59049 = 1047511 is prime, so 19 is in the sequence.

Links

Crossrefs

Cf. A006882, A007749, A094144, A123910, A258452, A258616, A262772, A261145.

Programs

  • Mathematica
    MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n - k, k]]];
Select[Range[17, 50000], PrimeQ[MultiFactorial[#, 3] - 3^10] &]
  • PARI
    tf(n) = prod(i=0, (n-1)\3, n-3*i);
for(n=1, 1e4, if(ispseudoprime(tf(n) - 3^10), print1(n , ", "))) \\ Altug Alkan, Dec 04 2015

A258866 Numbers k such that k!! - 1024 is prime.

Original entry on oeis.org

11, 17, 31, 39, 53, 93, 95, 381, 727, 867, 1229, 1573, 3161, 4293, 5635, 7077, 7093, 8861, 37401
Offset: 1

Views

Author

Robert Price, Nov 06 2015

Keywords

Comments

Corresponding primes are 9371, 34458401, ... .
a(20) > 50000.

Links

Crossrefs

Cf. A006882, A007749, A094144, A123910, A258452, A258616, A262772.

Programs

  • Mathematica
    Select[Range[0, 50000], If[#!! - 1024 > 0, PrimeQ[#!! - 1024]] &]

A259359 Numbers n such that n!!-8 is prime.

Original entry on oeis.org

5, 7, 9, 19, 41, 43, 83, 89, 91, 143, 299, 307, 341, 381, 585, 995, 1019, 1027, 2043, 4301, 6275, 11157, 11621, 12315, 17505, 24771, 30535, 38635
Offset: 1

Views

Author

Robert Price, Jun 24 2015

Keywords

Comments

Corresponding primes are 7, 97, 937, 654729067, 13113070457687988603440617, ... .
a(29) > 50000.

Links

Crossrefs

Cf. A006882, A007749, A094144, A123910, A258616.

Programs

  • Mathematica
    Select[Range[5,1000],PrimeQ[#!!-8]&]

A267029 Numbers n such that n!!! - 3^9 is prime, where n!3 = n!!! is a triple factorial number (A007661).

Original entry on oeis.org

16, 17, 34, 38, 49, 62, 74, 97, 125, 137, 146, 178, 188, 235, 664, 863, 916, 1988, 2059, 2837, 5353, 5489, 7483, 9344, 12631, 13796, 17122, 23134, 30409, 33077
Offset: 1

Views

Author

Robert Price, Jan 09 2016

Keywords

Comments

Corresponding primes are 38557, 189757, 17961239276317, 3091650738156317, ... .
a(31) > 50000.

Examples

			16!3 - 3^9 = 16*13*10*7*4*1 - 19683 = 58240 - 19683 = 38557 is prime, so 16 is in the sequence.

Links

Crossrefs

Cf. A006882, A007749, A094144, A123910, A258452, A258616, A262772, A261145, A265201.

Programs

  • Mathematica
    MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n - k, k]]];
Select[Range[15, 50000], PrimeQ[MultiFactorial[#, 3] - 3^9] &]
Select[Range[12,33100],PrimeQ[Times@@Range[#,1,-3]-19683]&] (* Harvey P. Dale, Jan 25 2021 *)

A289852 Primes of the form k!2 - 16, where k!2 is the double factorial number (A006882).

Original entry on oeis.org

89, 929, 135119, 34459409, 7905853580609, 669325572332691496707919692320662308340434243618803739488329723923351785805848442856791239207612629457179653299076271283992814866750698368061459208762618124485015869140609
Offset: 1

Views

Author

Robert Price, Jul 13 2017

Keywords

Links

Crossrefs

Cf. A006882, A258616.

Programs

  • Mathematica
    MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 2] - 16, {i, 6, 100}], PrimeQ[#]&]

Formula

a(n) = A006882(A258616(n)) - 16. - Elmo R. Oliveira, Apr 14 2025
Showing 1-7 of 7 results.

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

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