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.

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A329176 Numbers k such that k![4] - 128 is prime, where k![4] = A007662(k) = quadruple factorial.

Original entry on oeis.org

11, 13, 17, 19, 25, 27, 29, 41, 47, 61, 75, 113, 181, 251, 287, 339, 521, 533, 573, 687, 739, 1015, 1243, 1811, 2073, 2851, 2939, 3421, 4055, 4211, 4477, 5219, 6151, 8851, 9251, 14219, 17123, 21703, 24313, 25053, 28811, 33065, 49305, 50775, 52693, 69805, 82077, 87771
Offset: 1

Views

Author

Robert Price, Nov 07 2019

Keywords

Comments

a(49) > 10^5.
The first 5 primes associated with this sequence are: 103, 457, 9817, 65707, 5220997.

Crossrefs

Programs

  • Mathematica
    MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
    Select[Range[1000], (x = MultiFactorial[#, 4] - 128; x > 0 && PrimeQ[x]) &]
    Select[Range[10,90000],PrimeQ[Times@@Range[#,1,-4]-128]&] (* Harvey P. Dale, May 13 2022 *)

A329177 Numbers k such that k![4] - 256 is prime, where k![4] = A007662(k) = quadruple factorial.

Original entry on oeis.org

15, 17, 19, 21, 23, 25, 33, 39, 41, 43, 53, 63, 67, 73, 157, 167, 181, 195, 221, 327, 363, 419, 849, 861, 1233, 1265, 1599, 2413, 2515, 4009, 8291, 8475, 10685, 13957, 17453, 18409, 19117, 22739, 33313, 37861, 59703, 64983, 80697
Offset: 1

Views

Author

Robert Price, Nov 07 2019

Keywords

Comments

a(44) > 10^5.
The first 5 primes associated with this sequence are: 3209, 9689, 65579, 208589, 1513949.

Crossrefs

Programs

  • Mathematica
    MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
    Select[Range[1000], (x = MultiFactorial[#, 4] - 256; x > 0 && PrimeQ[x]) &]
    Select[Range[10,1600],PrimeQ[Times@@Range[#,1,-4]-256]&] (* The program generates the first 27 terms of the sequence. To generate more, increase the second Range constant but the program may take a long time to run. *) (* Harvey P. Dale, Aug 01 2022 *)

A329183 Numbers k such that k![4] - 512 is prime, where k![4] = A007662(k) = quadruple factorial.

Original entry on oeis.org

13, 15, 17, 19, 21, 23, 25, 35, 39, 47, 67, 71, 89, 93, 113, 153, 163, 185, 201, 267, 427, 491, 871, 1645, 3075, 3351, 3435, 5385, 7893, 10649, 15597, 44641, 50039, 57269, 67647, 83061, 89717
Offset: 1

Views

Author

Robert Price, Nov 07 2019

Keywords

Comments

a(38) > 10^5.
The first 5 primes associated with this sequence are: 73, 2953, 9433, 65323, 208333.

Crossrefs

Programs

  • Mathematica
    MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
    Select[Range[1000], (x = MultiFactorial[#, 4] - 512; x > 0 && PrimeQ[x]) &]

A329184 Numbers k such that k![4] - 1024 is prime, where k![4] = A007662(k) = quadruple factorial.

Original entry on oeis.org

15, 19, 21, 25, 27, 33, 47, 51, 55, 85, 95, 153, 163, 187, 191, 315, 335, 363, 375, 419, 433, 669, 873, 1097, 1113, 1235, 1819, 1969, 2043, 2391, 2493, 3639, 4433, 5527, 6423, 9441, 14099, 24607, 27057, 62271, 98079
Offset: 1

Views

Author

Robert Price, Nov 07 2019

Keywords

Comments

a(42) > 10^5.
The first 5 primes associated with this sequence are: 2441, 64811, 207821, 5220101, 40882511.

Crossrefs

Programs

  • Mathematica
    MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
    Select[Range[1000], (x = MultiFactorial[#, 4] - 1024; x > 0 && PrimeQ[x]) &]

A007661 Triple factorial numbers a(n) = n!!!, defined by a(n) = n*a(n-3), a(0) = a(1) = 1, a(2) = 2. Sometimes written n!3.

Original entry on oeis.org

1, 1, 2, 3, 4, 10, 18, 28, 80, 162, 280, 880, 1944, 3640, 12320, 29160, 58240, 209440, 524880, 1106560, 4188800, 11022480, 24344320, 96342400, 264539520, 608608000, 2504902400, 7142567040, 17041024000, 72642169600, 214277011200, 528271744000, 2324549427200
Offset: 0

Views

Author

Keywords

Comments

The triple factorial of a positive integer n is the product of the positive integers <= n that have the same residue modulo 3 as n. - Peter Luschny, Jun 23 2011

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • J. Spanier and K. B. Oldham, An Atlas of Functions, Hemisphere, NY, 1987, p. 23.

Crossrefs

Programs

  • GAP
    a:= function(n)
        if n<3 then return Fibonacci(n+1);
        else return n*a(n-3);
        fi;
      end;
    List([0..30], n-> a(n) ); # G. C. Greubel, Aug 21 2019
  • Haskell
    a007661 n k = a007661_list !! n
    a007661_list = 1 : 1 : 2 : zipWith (*) a007661_list [3..]
    -- Reinhard Zumkeller, Sep 20 2013
    
  • Magma
    I:=[1,1,2];[n le 3 select I[n] else (n-1)*Self(n-3): n in [1..30]]; // Vincenzo Librandi, Nov 27 2015
    
  • Maple
    A007661 := n -> mul(k, k = select(k -> k mod 3 = n mod 3, [$1 .. n])): seq(A007661(n), n = 0 .. 29);  # Peter Luschny, Jun 23 2011
  • Mathematica
    multiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*multiFactorial[n - k, k]]]; Array[ multiFactorial[#, 3] &, 30, 0] (* Robert G. Wilson v, Apr 23 2011 *)
    RecurrenceTable[{a[0]==a[1]==1,a[2]==2,a[n]==n*a[n-3]},a,{n,30}] (* Harvey P. Dale, May 17 2012 *)
    Table[With[{q = Quotient[n + 2, 3]}, 3^q q! Binomial[n/3, q]], {n, 0, 30}] (* Jan Mangaldan, Mar 21 2013 *)
    a[ n_] := With[{m = Mod[n, 3, 1], q = 1 + Quotient[n, 3, 1]}, If[n < 0, 0, 3^q Pochhammer[m/3, q]]]; (* Michael Somos, Feb 24 2019 *)
    Table[Times@@Range[n,1,-3],{n,0,30}] (* Harvey P. Dale, Sep 12 2020 *)
  • PARI
    A007661(n,d=3)=prod(i=0,(n-1)\d,n-d*i) \\ M. F. Hasler, Feb 16 2008
    
  • Sage
    def a(n):
        if (n<3): return fibonacci(n+1)
        else: return n*a(n-3)
    [a(n) for n in (0..30)] # G. C. Greubel, Aug 21 2019
    

Formula

a(n) = Product_{i=0..floor((n-1)/3)} (n-3*i). - M. F. Hasler, Feb 16 2008
a(n) ~ c * n^(n/3+1/2)/exp(n/3), where c = sqrt(2*Pi/3) if n=3*k, c = sqrt(2*Pi)*3^(1/6) / Gamma(1/3) if n=3*k+1, c = sqrt(2*Pi)*3^(-1/6) / Gamma(2/3) if n=3*k+2. - Vaclav Kotesovec, Jul 29 2013
a(3*n) = A032031(n); a(3*n+1) = A007559(n+1); a(3*n+2) = A008544(n+1). - Reinhard Zumkeller, Sep 20 2013
0 = a(n)*(a(n+1) -a(n+4)) +a(n+1)*a(n+3) for all n>=0. - Michael Somos, Feb 24 2019
Sum_{n>=0} 1/a(n) = A288055. - Amiram Eldar, Nov 10 2020

A085158 Sextuple factorials, 6-factorials, n!!!!!!, n!6.

Original entry on oeis.org

1, 1, 2, 3, 4, 5, 6, 7, 16, 27, 40, 55, 72, 91, 224, 405, 640, 935, 1296, 1729, 4480, 8505, 14080, 21505, 31104, 43225, 116480, 229635, 394240, 623645, 933120, 1339975, 3727360, 7577955, 13404160, 21827575, 33592320, 49579075, 141639680
Offset: 0

Views

Author

Hugo Pfoertner, Jun 21 2003

Keywords

Comments

The term "Sextuple factorial numbers" is also used for the sequences A008542, A008543, A011781, A047058, A047657, A049308, which have a different definition. The definition given here is the one commonly used.

Examples

			a(14) = 224 because 14*a(14-6) = 14*a(8) = 14*16 = 224.
		

Crossrefs

Cf. n!:A000142, n!!:A006882, n!!!:A007661, n!!!!:A007662, n!!!!!:A085157, 6-factorial primes: n!!!!!!+1:A085150, n!!!!!!-1:A051592.
Cf. A288093.

Programs

  • GAP
    a:= function(n)
        if n<1 then return 1;
        else return n*a(n-6);
        fi;
      end;
    List([0..40], n-> a(n) ); # G. C. Greubel, Aug 21 2019
  • Magma
    b:=func< n | n le 6 select n else n*Self(n-6) >;
    [1] cat [b(n): n in [1..40]]; // G. C. Greubel, Aug 21 2019
    
  • Maple
    a:= n-> `if`(n<1, 1, n*a(n-6)); seq(a(n), n=0..40); # G. C. Greubel, Aug 21 2019
  • Mathematica
    Table[Times@@Range[n,1,-6],{n,0,40}] (* Harvey P. Dale, Aug 10 2019 *)
  • PARI
    a(n)=if(n<1, 1, n*a(n-6));
    vector(40, n, n--; a(n) ) \\ G. C. Greubel, Aug 21 2019
    
  • Sage
    def a(n):
        if (n<1): return 1
        else: return n*a(n-6)
    [a(n) for n in (0..40)] # G. C. Greubel, Aug 21 2019
    

Formula

a(n)=1 for n < 1, otherwise a(n) = n*a(n-6).
Sum_{n>=0} 1/a(n) = A288093. - Amiram Eldar, Nov 10 2020

A008542 Sextuple factorial numbers: Product_{k=0..n-1} (6*k+1).

Original entry on oeis.org

1, 1, 7, 91, 1729, 43225, 1339975, 49579075, 2131900225, 104463111025, 5745471106375, 350473737488875, 23481740411754625, 1714167050058087625, 135419196954588922375, 11510631741140058401875, 1047467488443745314570625, 101604346379043295513350625
Offset: 0

Views

Author

Joe Keane (jgk(AT)jgk.org)

Keywords

Comments

a(n), n>=1, enumerates increasing heptic (7-ary) trees with n vertices. - Wolfdieter Lang, Sep 14 2007; see a D. Callan comment on A007559 (number of increasing quarterny trees).

Crossrefs

Programs

  • GAP
    List([0..20], n-> Product([0..n-1], k-> (6*k+1) )); # G. C. Greubel, Aug 17 2019
  • Magma
    [1] cat [(&*[(6*k+1): k in [0..n-1]]): n in [1..20]]; // G. C. Greubel, Aug 17 2019
    
  • Maple
    a := n -> mul(6*k+1, k=0..n-1);
    G(x):=(1-6*x)^(-1/6): f[0]:=G(x): for n from 1 to 29 do f[n]:=diff(f[n-1],x) od: x:=0: seq(f[n],n=0..15); # Zerinvary Lajos, Apr 03 2009
  • Mathematica
    Table[Product[(6*k+1), {k,0,n-1}], {n,0,20}] (* Vladimir Joseph Stephan Orlovsky, Nov 08 2008, modified by G. C. Greubel, Aug 17 2019 *)
    FoldList[Times, 1, 6Range[0, 20] + 1] (* Vincenzo Librandi, Jun 10 2013 *)
    Table[6^n*Pochhammer[1/6, n], {n,0,20}] (* G. C. Greubel, Aug 17 2019 *)
  • PARI
    a(n)=prod(k=1,n-1,6*k+1) \\ Charles R Greathouse IV, Jul 19 2011
    
  • Sage
    [product((6*k+1) for k in (0..n-1)) for n in (0..20)] # G. C. Greubel, Aug 17 2019
    

Formula

E.g.f.: (1-6*x)^(-1/6).
a(n) ~ 2^(1/2)*Pi^(1/2)*Gamma(1/6)^-1*n^(-1/3)*6^n*e^-n*n^n*{1 + 1/72*n^-1 - ...}. - Joe Keane (jgk(AT)jgk.org), Nov 24 2001
a(n) = Sum_{k=0..n} (-6)^(n-k)*A048994(n, k). - Philippe Deléham, Oct 29 2005
G.f.: 1+x/(1-7x/(1-6x/(1-13x/(1-12x/(1-19x/(1-18x/(1-25x/(1-24x/(1-... (continued fraction). - Philippe Deléham, Jan 08 2012
a(n) = (-5)^n*Sum_{k=0..n} (6/5)^k*s(n+1,n+1-k), where s(n,k) are the Stirling numbers of the first kind, A048994. - Mircea Merca, May 03 2012
G.f.: 1/Q(0) where Q(k) = 1 - x*(6*k+1)/(1 - x*(6*k+6)/Q(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Mar 20 2013
a(n) = A085158(6*n-5). - M. F. Hasler, Feb 23 2018
D-finite with recurrence: a(n) +(-6*n+5)*a(n-1)=0. - R. J. Mathar, Jan 17 2020
Sum_{n>=0} 1/a(n) = 1 + (e/6^5)^(1/6)*(Gamma(1/6) - Gamma(1/6, 1/6)). - Amiram Eldar, Dec 18 2022

A045754 7-fold factorials: a(n) = Product_{k=0..n-1} (7*k+1).

Original entry on oeis.org

1, 1, 8, 120, 2640, 76560, 2756160, 118514880, 5925744000, 337767408000, 21617114112000, 1534815101952000, 119715577952256000, 10175824125941760000, 936175819586641920000, 92681406139077550080000, 9824229050742220308480000, 1110137882733870894858240000
Offset: 0

Views

Author

Keywords

Crossrefs

See also A113134.
Unsigned row sums of triangle A051186 (scaled Stirling1).
First column of triangle A132056 (S2(8)).

Programs

  • GAP
    List([0..20], n-> Product([0..n-1], k-> 7*k+1) ); # G. C. Greubel, Aug 21 2019
  • Magma
    [1] cat [&*[7*j+1: j in [0..n-1]]: n in [1..20]]; // G. C. Greubel, Aug 21 2019
    
  • Maple
    f := n->product( (7*k+1), k=0..(n-1));
    G(x):=(1-7*x)^(-1/7): f[0]:=G(x): for n from 1 to 29 do f[n]:=diff(f[n-1],x) od: x:=0: seq(f[n],n=0..14); # Zerinvary Lajos, Apr 03 2009
  • Mathematica
    FoldList[Times, 1, 7Range[0, 20] + 1] (* Harvey P. Dale, Jan 21 2013 *)
  • PARI
    a(n)=prod(k=0,n-1,7*k+1)
    
  • Sage
    [7^n*rising_factorial(1/7, n) for n in (0..20)] # G. C. Greubel, Aug 21 2019
    

Formula

a(n) = Sum_{k=0..n} (-7)^(n-k)*A048994(n, k), where A048994 = Stirling-1 numbers.
E.g.f.: (1-7*x)^(-1/7).
G.f.: 1/(1-x/(1-7*x/(1-8*x/(1-14*x/(1-15*x/(1-21*x/(1-22*x/(1-... (continued fraction). - Philippe Deléham, Jan 08 2012
a(n) = (-6)^n*Sum_{k=0..n} (7/6)^k*s(n+1,n+1-k), where s(n,k) are the Stirling numbers of the first kind, A048994. - Mircea Merca, May 03 2012
G.f.: 1/G(0), where G(k)= 1 - x*(7*k+1)/(1 - x*(7*k+7)/G(k+1)); (continued fraction). - Sergei N. Gladkovskii, Jun 05 2013
G.f.: G(0)/2, where G(k)= 1 + 1/(1 - x*(7*k+1)/(x*(7*k+1) + 1/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, Jun 05 2013
a(n) = 7^n * Gamma(n + 1/7) / Gamma(1/7). - Artur Jasinski, Aug 23 2016
a(n) = A114799(7n-6). - M. F. Hasler, Feb 23 2018
D-finite with recurrence: a(n) +(-7*n+6)*a(n-1)=0. - R. J. Mathar, Jan 17 2020
Sum_{n>=0} 1/a(n) = 1 + (e/7^6)^(1/7)*(Gamma(1/7) - Gamma(1/7, 1/7)). - Amiram Eldar, Dec 19 2022

Extensions

Additional comments from Philippe Deléham and Paul D. Hanna, Oct 29 2005
Edited by N. J. A. Sloane, Oct 16 2008 at the suggestion of M. F. Hasler, Oct 14 2008
Corrected by Zerinvary Lajos, Apr 03 2009

A085157 Quintuple factorials, 5-factorials, n!!!!!, n!5.

Original entry on oeis.org

1, 1, 2, 3, 4, 5, 6, 14, 24, 36, 50, 66, 168, 312, 504, 750, 1056, 2856, 5616, 9576, 15000, 22176, 62832, 129168, 229824, 375000, 576576, 1696464, 3616704, 6664896, 11250000, 17873856, 54286848, 119351232, 226606464, 393750000, 643458816
Offset: 0

Views

Author

Hugo Pfoertner, Jun 21 2003

Keywords

Comments

The term "Quintuple factorial numbers" is also used for the sequences A008546, A008548, A052562, A047055, A047056 which have a different definition. The definition given here is the one commonly used.

Examples

			a(12) = 168 because 12*a(12-5) = 12*a(7) = 12*14 = 168.
		

Crossrefs

Cf. n!:A000142, n!!:A006882, n!!!:A007661, n!!!!:A007662, n!!!!!!:A085158, 5-factorial primes: n!!!!!+1:A085148, n!!!!!-1:A085149.
Cf. A288092.

Programs

  • GAP
    a:= function(n)
        if n<1 then return 1;
        else return n*a(n-5);
        fi;
      end;
    List([0..40], n-> a(n) ); # G. C. Greubel, Aug 18 2019
    
  • Magma
    b:= func< n | (n lt 6) select n else n*Self(n-5) >;
    [1] cat [b(n): n in [1..40]]; // G. C. Greubel, Aug 18 2019
    
  • Maple
    a:= n-> `if`(n < 1, 1, n*a(n-5)) end proc; seq(a(n), n = 0..40); # G. C. Greubel, Aug 18 2019
  • Mathematica
    a[n_]:= If[n<1, 1, n*a[n-5]]; Table[a[n], {n,0,40}] (* G. C. Greubel, Aug 18 2019 *)
    Table[Times@@Range[n,1,-5],{n,0,40}] (* Harvey P. Dale, May 12 2020 *)
  • PARI
    a(n)=if(n<1, 1, n*a(n-5))
    for(n=0,50,print1(a(n),",")) \\ Herman Jamke (hermanjamke(AT)fastmail.fm), Oct 19 2006
    
  • Python
    def A085157(n):
        if n <= 0:
            return 1
        else:
            return n*A085157(n-5)
    n = 0
    while n <= 40:
        print(n,A085157(n))
        n = n+1 # A.H.M. Smeets, Aug 18 2019
  • Sage
    def a(n):
        if (n<1): return 1
        else: return n*a(n-5)
    [a(n) for n in (0..40)] # G. C. Greubel, Aug 18 2019
    

Formula

a(n) = 1 for n < 1, otherwise a(n) = n*a(n-5).
Sum_{n>=0} 1/a(n) = A288092. - Amiram Eldar, Nov 10 2020

A114800 Octuple factorial, 8-factorial, n!8, n!!!!!!!!.

Original entry on oeis.org

1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 20, 33, 48, 65, 84, 105, 128, 153, 360, 627, 960, 1365, 1848, 2415, 3072, 3825, 9360, 16929, 26880, 39585, 55440, 74865, 98304, 126225, 318240, 592515, 967680, 1464645, 2106720, 2919735, 3932160, 5175225, 13366080
Offset: 0

Views

Author

Jonathan Vos Post, Feb 18 2006

Keywords

Examples

			a(10) = 10 * a(10-8) = 10 * a(2) = 10 * 2 = 20.
a(20) = 20 * a(20-8) = 20 * a(12) = 20 * (12*a(12-8)) = 20 * 12 * a(4) = 20 * 12 * 4 = 960.
a(30) = 30 * a(30-8) = 30 * a(22) = 30 * (22*a(22-8)) = 30 * 22 * a(14) = 30 * 22 * (14*a(14-8)) = 30 * 22 * 14 * 6 = 55440.
		

Crossrefs

Programs

  • GAP
    a:= function(n)
        if n<1 then return 1;
        else return n*a(n-8);
        fi;
      end;
    List([0..50], n-> a(n) ); # G. C. Greubel, Aug 21 2019
  • Magma
    b:=func< n | n le 8 select n else n*Self(n-8) >;
    [1] cat [b(n): n in [1..50]]; // G. C. Greubel, Aug 21 2019
    
  • Maple
    A114800 := proc(n)
        option remember;
        if n < 1 then
            1;
        else
            n*procname(n-8) ;
        end if;
    end proc:
    seq(A114800(n),n=0..40) ; # R. J. Mathar, Jun 23 2014
  • Mathematica
    Table[Times@@Range[n,1,-8],{n,0,50}] (* Harvey P. Dale, Feb 17 2018 *)
  • PARI
    a(n)=if(n<1, 1, n*a(n-8));
    vector(50, n, n--; a(n) ) \\ G. C. Greubel, Aug 21 2019
    
  • Sage
    def a(n):
        if (n<1): return 1
        else: return n*a(n-8)
    [a(n) for n in (0..50)] # G. C. Greubel, Aug 21 2019
    

Formula

a(n) = 1 for n<1, else a(n) = n*a(n-8).
Sum_{n>=0} 1/a(n) = A288095. - Amiram Eldar, Nov 10 2020
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