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 1-9 of 9 results.

A022915 Multinomial coefficients (0, 1, ..., n)! = C(n+1,2)!/(0!*1!*2!*...*n!).

Original entry on oeis.org

1, 1, 3, 60, 12600, 37837800, 2053230379200, 2431106898187968000, 73566121315513295589120000, 65191584694745586153436251091200000, 1906765806522767212441719098019963758016000000, 2048024348726152339387799085049745725891853852479488000000
Offset: 0

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Author

Keywords

Comments

Number of ways to put numbers 1, 2, ..., n*(n+1)/2 in a triangular array of n rows in such a way that each row is increasing. Also number of ways to choose groups of 1, 2, 3, ..., n-1 and n objects out of n*(n+1)/2 objects. - Floor van Lamoen, Jul 16 2001
a(n) is the number of ways to linearly order the multiset {1,2,2,3,3,3,...n,n,...n}. - Geoffrey Critzer, Mar 08 2009
Also the number of distinct adjacency matrices in the n-triangular honeycomb rook graph. - Eric W. Weisstein, Jul 14 2017

Examples

			From _Gus Wiseman_, Aug 12 2020: (Start)
The a(3) = 60 permutations of the prime indices of A006939(3) = 360:
  (111223)  (121123)  (131122)  (212113)  (231211)
  (111232)  (121132)  (131212)  (212131)  (232111)
  (111322)  (121213)  (131221)  (212311)  (311122)
  (112123)  (121231)  (132112)  (213112)  (311212)
  (112132)  (121312)  (132121)  (213121)  (311221)
  (112213)  (121321)  (132211)  (213211)  (312112)
  (112231)  (122113)  (211123)  (221113)  (312121)
  (112312)  (122131)  (211132)  (221131)  (312211)
  (112321)  (122311)  (211213)  (221311)  (321112)
  (113122)  (123112)  (211231)  (223111)  (321121)
  (113212)  (123121)  (211312)  (231112)  (321211)
  (113221)  (123211)  (211321)  (231121)  (322111)
(End)
		

Crossrefs

A190945 counts the case of anti-run permutations.
A317829 counts partitions of this multiset.
A325617 is the version for factorials instead of superprimorials.
A006939 lists superprimorials or Chernoff numbers.
A008480 counts permutations of prime indices.
A181818 gives products of superprimorials, with complement A336426.

Programs

  • Maple
    with(combinat):
    a:= n-> multinomial(binomial(n+1, 2), $0..n):
    seq(a(n), n=0..12);  # Alois P. Heinz, May 18 2013
  • Mathematica
    Table[Apply[Multinomial ,Range[n]], {n, 0, 20}]  (* Geoffrey Critzer, Dec 09 2012 *)
    Table[Multinomial @@ Range[n], {n, 0, 20}] (* Eric W. Weisstein, Jul 14 2017 *)
    Table[Binomial[n + 1, 2]!/BarnesG[n + 2], {n, 0, 20}] (* Eric W. Weisstein, Jul 14 2017 *)
    Table[Length[Permutations[Join@@Table[i,{i,n},{i}]]],{n,0,4}] (* Gus Wiseman, Aug 12 2020 *)
  • PARI
    a(n) = binomial(n+1,2)!/prod(k=1, n, k^(n+1-k)); \\ Michel Marcus, May 02 2019

Formula

a(n) = (n*(n+1)/2)!/(0!*1!*2!*...*n!).
a(n) = a(n-1) * A014068(n). - Dan Fux (dan.fux(AT)OpenGaia.com or danfux(AT)OpenGaia.com), Apr 08 2001.
a(n) = A052295(n)/A000178(n). - Lekraj Beedassy, Feb 19 2004
a(n) = A208437(n*(n+1)/2,n). - Alois P. Heinz, Apr 08 2016
a(n) ~ A * exp(n^2/4 + n + 1/6) * n^(n^2/2 + 7/12) / (2^((n+1)^2/2) * Pi^(n/2)), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, May 02 2019
a(n) = A327803(n*(n+1)/2,n). - Alois P. Heinz, Sep 25 2019
a(n) = A008480(A006939(n)). - Gus Wiseman, Aug 12 2020

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Apr 11 2001
More terms from Michel ten Voorde, Apr 12 2001
Better definition from L. Edson Jeffery, May 18 2013

A317829 Number of set partitions of multiset {1, 2, 2, 3, 3, 3, ..., n X n}.

Original entry on oeis.org

1, 1, 4, 52, 2776, 695541, 927908528, 7303437156115, 371421772559819369, 132348505150329265211927, 355539706668772869353964510735, 7698296698535929906799439134946965681, 1428662247641961794158621629098030994429958386, 2405509035205023556420199819453960482395657232596725626
Offset: 0

Views

Author

Antti Karttunen, Aug 10 2018

Keywords

Comments

Number of factorizations of the superprimorial A006939(n) into factors > 1. - Gus Wiseman, Aug 21 2020

Examples

			For n = 2 we have a multiset {1, 2, 2} which can be partitioned as {{1}, {2}, {2}} or {{1, 2}, {2}} or {{1}, {2, 2}} or {{1, 2, 2}}, thus a(2) = 4.
		

Crossrefs

Subsequence of A317828.
A000142 counts submultisets of the same multiset.
A022915 counts permutations of the same multiset.
A337069 is the strict case.
A001055 counts factorizations.
A006939 lists superprimorials or Chernoff numbers.
A076716 counts factorizations of factorials.
A076954 can be used instead of A006939 (cf. A307895, A325337).
A181818 lists products of superprimorials, with complement A336426.

Programs

  • Maple
    g:= proc(n, k) option remember; uses numtheory; `if`(n>k, 0, 1)+
         `if`(isprime(n), 0, add(`if`(d>k or max(factorset(n/d))>d, 0,
            g(n/d, d)), d=divisors(n) minus {1, n}))
        end:
    a:= n-> g(mul(ithprime(i)^i, i=1..n)$2):
    seq(a(n), n=0..5);  # Alois P. Heinz, Jul 26 2020
  • Mathematica
    chern[n_]:=Product[Prime[i]^(n-i+1),{i,n}];
    facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]];
    Table[Length[facs[chern[n]]],{n,3}] (* Gus Wiseman, Aug 21 2020 *)
  • PARI
    \\ See A318284 for count.
    a(n) = {if(n==0, 1, count(vector(n,i,i)))} \\ Andrew Howroyd, Aug 31 2020

Formula

a(n) = A317826(A033312(n+1)) = A317826((n+1)!-1) = A001055(A076954(n)).
a(n) = A001055(A006939(n)). - Gus Wiseman, Aug 21 2020
a(n) = A318284(A002110(n)). - Andrew Howroyd, Aug 31 2020

Extensions

a(0)=1 prepended and a(7) added by Alois P. Heinz, Jul 26 2020
a(8)-a(13) from Andrew Howroyd, Aug 31 2020

A336496 Products of superfactorials (A000178).

Original entry on oeis.org

1, 2, 4, 8, 12, 16, 24, 32, 48, 64, 96, 128, 144, 192, 256, 288, 384, 512, 576, 768, 1024, 1152, 1536, 1728, 2048, 2304, 3072, 3456, 4096, 4608, 6144, 6912, 8192, 9216, 12288, 13824, 16384, 18432, 20736, 24576, 27648, 32768, 34560, 36864, 41472, 49152, 55296
Offset: 1

Views

Author

Gus Wiseman, Aug 03 2020

Keywords

Comments

First differs from A317804 in having 34560, which is the first term with more than two distinct prime factors.

Examples

			The sequence of terms together with their prime indices begins:
    1: {}
    2: {1}
    4: {1,1}
    8: {1,1,1}
   12: {1,1,2}
   16: {1,1,1,1}
   24: {1,1,1,2}
   32: {1,1,1,1,1}
   48: {1,1,1,1,2}
   64: {1,1,1,1,1,1}
   96: {1,1,1,1,1,2}
  128: {1,1,1,1,1,1,1}
  144: {1,1,1,1,2,2}
  192: {1,1,1,1,1,1,2}
  256: {1,1,1,1,1,1,1,1}
  288: {1,1,1,1,1,2,2}
  384: {1,1,1,1,1,1,1,2}
  512: {1,1,1,1,1,1,1,1,1}
		

Crossrefs

A001013 is the version for factorials, with complement A093373.
A181818 is the version for superprimorials, with complement A336426.
A336497 is the complement.
A000178 lists superfactorials.
A001055 counts factorizations.
A006939 lists superprimorials or Chernoff numbers.
A049711 is the minimum prime multiplicity in A000178.
A174605 is the maximum prime multiplicity in A000178.
A303279 counts prime factors of superfactorials.
A317829 counts factorizations of superprimorials.
A322583 counts factorizations into factorials.
A325509 counts factorizations of factorials into factorials.

Programs

  • Mathematica
    supfac[n_]:=Product[k!,{k,n}];
    facsusing[s_,n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facsusing[Select[s,Divisible[n/d,#]&],n/d],Min@@#>=d&]],{d,Select[s,Divisible[n,#]&]}]];
    Select[Range[1000],facsusing[Rest[Array[supfac,30]],#]!={}&]

A337069 Number of strict factorizations of the superprimorial A006939(n).

Original entry on oeis.org

1, 1, 3, 34, 1591, 360144, 442349835, 3255845551937, 156795416820025934, 53452979022001011490033, 138542156296245533221812350867, 2914321438328993304235584538307144802, 528454951438415221505169213611461783474874149, 873544754831735539240447436467067438924478174290477803
Offset: 0

Views

Author

Gus Wiseman, Aug 15 2020

Keywords

Comments

The n-th superprimorial is A006939(n) = Product_{i = 1..n} prime(i)^(n - i + 1).
Also the number of strict multiset partitions of {1,2,2,3,3,3,...,n}, a multiset with i copies of i for i = 1..n.

Examples

			The a(3) = 34 factorizations:
  2*3*4*15  2*3*60   2*180  360
  2*3*5*12  2*4*45   3*120
  2*3*6*10  2*5*36   4*90
  2*4*5*9   2*6*30   5*72
  3*4*5*6   2*9*20   6*60
            2*10*18  8*45
            2*12*15  9*40
            3*4*30   10*36
            3*5*24   12*30
            3*6*20   15*24
            3*8*15   18*20
            3*10*12
            4*5*18
            4*6*15
            4*9*10
            5*6*12
            5*8*9
		

Crossrefs

A022915 counts permutations of the same multiset.
A157612 is the version for factorials instead of superprimorials.
A317829 is the non-strict version.
A337072 is the non-strict version with squarefree factors.
A337073 is the case with squarefree factors.
A000217 counts prime factors (with multiplicity) of superprimorials.
A001055 counts factorizations.
A006939 lists superprimorials or Chernoff numbers.
A045778 counts strict factorizations.
A076954 can be used instead of A006939 (cf. A307895, A325337).
A181818 lists products of superprimorials, with complement A336426.
A322583 counts factorizations into factorials.

Programs

  • Mathematica
    chern[n_]:=Product[Prime[i]^(n-i+1),{i,n}];
    stfa[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[stfa[n/d],Min@@#>d&]],{d,Rest[Divisors[n]]}]];
    Table[Length[stfa[chern[n]]],{n,0,3}]
  • PARI
    \\ See A318286 for count.
    a(n) = {if(n==0, 1, count(vector(n, i, i)))} \\ Andrew Howroyd, Sep 01 2020

Formula

a(n) = A045778(A006939(n)).
a(n) = A318286(A002110(n)). - Andrew Howroyd, Sep 01 2020

Extensions

a(7)-a(13) from Andrew Howroyd, Sep 01 2020

A303281 Expansion of (x/(1 - x)) * (d/dx) Sum_{p prime, k>=1} x^(p^k)/(1 - x^(p^k)).

Original entry on oeis.org

0, 2, 5, 13, 18, 30, 37, 61, 79, 99, 110, 146, 159, 187, 217, 281, 298, 352, 371, 431, 473, 517, 540, 636, 686, 738, 819, 903, 932, 1022, 1053, 1213, 1279, 1347, 1417, 1561, 1598, 1674, 1752, 1912, 1953, 2079, 2122, 2254, 2389, 2481, 2528, 2768, 2866, 3016, 3118, 3274, 3327, 3543, 3653
Offset: 1

Views

Author

Ilya Gutkovskiy, Apr 20 2018

Keywords

Comments

Sum of exponents in prime-power factorization of hyperfactorial: Product_{k=1..n} k^k (A002109).
Partial sums of A066959.

Examples

			a(4) = 13 because 2^2*3^3*4^4 = 2^10*3^3 and 10 + 3 = 13.
		

Crossrefs

Programs

  • Mathematica
    nmax = 55; Rest[CoefficientList[Series[x/(1 - x) D[Sum[Boole[PrimePowerQ[k]] x^k/(1 - x^k), {k, 1, nmax}], x], {x, 0, nmax}], x]]
    Table[PrimeOmega[Hyperfactorial[n]], {n, 55}]
    Table[Sum[k PrimeOmega[k], {k, n}], {n, 55}]
    Accumulate[Table[k * PrimeOmega[k], {k, 1, 55}]] (* Amiram Eldar, Jun 13 2025 *)
  • PARI
    a(n) = sum(k=1, n, k*bigomega(k)); \\ Altug Alkan, Apr 20 2018

A336497 Numbers that cannot be written as a product of superfactorials A000178.

Original entry on oeis.org

3, 5, 6, 7, 9, 10, 11, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76
Offset: 1

Views

Author

Gus Wiseman, Aug 03 2020

Keywords

Comments

First differs from A336426 in having 360.

Examples

			The sequence of terms together with their prime indices begins:
     3: {2}        22: {1,5}        39: {2,6}
     5: {3}        23: {9}          40: {1,1,1,3}
     6: {1,2}      25: {3,3}        41: {13}
     7: {4}        26: {1,6}        42: {1,2,4}
     9: {2,2}      27: {2,2,2}      43: {14}
    10: {1,3}      28: {1,1,4}      44: {1,1,5}
    11: {5}        29: {10}         45: {2,2,3}
    13: {6}        30: {1,2,3}      46: {1,9}
    14: {1,4}      31: {11}         47: {15}
    15: {2,3}      33: {2,5}        49: {4,4}
    17: {7}        34: {1,7}        50: {1,3,3}
    18: {1,2,2}    35: {3,4}        51: {2,7}
    19: {8}        36: {1,1,2,2}    52: {1,1,6}
    20: {1,1,3}    37: {12}         53: {16}
    21: {2,4}      38: {1,8}        54: {1,2,2,2}
		

Crossrefs

A093373 is the version for factorials, with complement A001013.
A336426 is the version for superprimorials, with complement A181818.
A336496 is the complement.
A000178 lists superfactorials.
A001055 counts factorizations.
A006939 lists superprimorials or Chernoff numbers.
A049711 is the minimum prime multiplicity in A000178(n).
A174605 is the maximum prime multiplicity in A000178(n).
A303279 counts prime factors (with multiplicity) of superprimorials.
A317829 counts factorizations of superprimorials.
A322583 counts factorizations into factorials.
A325509 counts factorizations of factorials into factorials.

Programs

  • Mathematica
    supfac[n_]:=Product[k!,{k,n}];
    facsusing[s_,n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facsusing[Select[s,Divisible[n/d,#]&],n/d],Min@@#>=d&]],{d,Select[s,Divisible[n,#]&]}]];
    Select[Range[100],facsusing[Rest[Array[supfac,30]],#]=={}&]

A337072 Number of factorizations of the superprimorial A006939(n) into squarefree numbers > 1.

Original entry on oeis.org

1, 1, 2, 10, 141, 6769, 1298995, 1148840085, 5307091649182, 143026276277298216, 24801104674619158730662, 30190572492693121799801655311, 278937095127086600900558327826721594
Offset: 0

Views

Author

Gus Wiseman, Aug 15 2020

Keywords

Comments

The n-th superprimorial is A006939(n) = Product_{i = 1..n} prime(i)^(n - i + 1), which has n! divisors.
Also the number of set multipartitions (multisets of sets) of the multiset of prime factors of the superprimorial A006939(n).

Examples

			The a(1) = 1 through a(3) = 10 factorizations:
    2  2*6    2*6*30
       2*2*3  6*6*10
              2*5*6*6
              2*2*3*30
              2*2*6*15
              2*3*6*10
              2*2*3*5*6
              2*2*2*3*15
              2*2*3*3*10
              2*2*2*3*3*5
The a(1) = 1 through a(3) = 10 set multipartitions:
     {1}  {1}{12}    {1}{12}{123}
          {1}{1}{2}  {12}{12}{13}
                     {1}{1}{12}{23}
                     {1}{1}{2}{123}
                     {1}{2}{12}{13}
                     {1}{3}{12}{12}
                     {1}{1}{1}{2}{23}
                     {1}{1}{2}{2}{13}
                     {1}{1}{2}{3}{12}
                     {1}{1}{1}{2}{2}{3}
		

Crossrefs

A000142 counts divisors of superprimorials.
A022915 counts permutations of the same multiset.
A103774 is the version for factorials instead of superprimorials.
A337073 is the strict case (strict factorizations into squarefree numbers).
A001055 counts factorizations.
A006939 lists superprimorials or Chernoff numbers.
A045778 counts strict factorizations.
A050320 counts factorizations into squarefree numbers.
A050326 counts strict factorizations into squarefree numbers.
A076954 can be used instead of A006939 (cf. A307895, A325337).
A089259 counts set multipartitions of integer partitions.
A116540 counts normal set multipartitions.
A317829 counts factorizations of superprimorials.
A337069 counts strict factorizations of superprimorials.

Programs

  • Mathematica
    chern[n_]:=Product[Prime[i]^(n-i+1),{i,n}];
    facsqf[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facsqf[n/d],Min@@#>=d&]],{d,Select[Rest[Divisors[n]],SquareFreeQ]}]];
    Table[Length[facsqf[chern[n]]],{n,0,3}]
  • PARI
    \\ See A318360 for count.
    a(n) = {if(n==0, 1, count(vector(n,i,i)))} \\ Andrew Howroyd, Aug 31 2020

Formula

a(n) = A050320(A006939(n)).
a(n) = A318360(A002110(n)). - Andrew Howroyd, Aug 31 2020

Extensions

a(7)-a(12) from Andrew Howroyd, Aug 31 2020

A356718 T(n,k) is the total number of prime factors, counted with multiplicity, of k!*(n-k)!, for 0 <= k <= n. Triangle read by rows.

Original entry on oeis.org

0, 0, 0, 1, 0, 1, 2, 1, 1, 2, 4, 2, 2, 2, 4, 5, 4, 3, 3, 4, 5, 7, 5, 5, 4, 5, 5, 7, 8, 7, 6, 6, 6, 6, 7, 8, 11, 8, 8, 7, 8, 7, 8, 8, 11, 13, 11, 9, 9, 9, 9, 9, 9, 11, 13, 15, 13, 12, 10, 11, 10, 11, 10, 12, 13, 15, 16, 15, 14, 13, 12, 12, 12
Offset: 0

Views

Author

Dario T. de Castro, Aug 24 2022

Keywords

Comments

k!*(n-k)! is the denominator in binomial(n,k) = n!/(k!*(n-k)!) and all prime factors in the denominator cancel to leave an integer, so that T(n,k) = A022559(n) - A132896(n,k).

Examples

			Triangle begins:
  n\k| 0  1  2  3  4  5  6  7
  ---+--------------------------------------
   0 | 0
   1 | 0, 0;
   2 | 1, 0, 1;
   3 | 2, 1, 1, 2;
   4 | 4, 2, 2, 2, 4;
   5 | 5, 4, 3, 3, 4, 5;
		

Crossrefs

Programs

  • Mathematica
    T[n_,k_]:=PrimeOmega[Factorial[k]*Factorial[n-k]];
    tab=Flatten[Table[T[n,k],{n,0,10},{k,0,n}]]

Formula

T(n,k) = bigomega(k!*(n-k)!), where 0 <= k <= n.
T(n,0) = T(n,n) = A022559(n).

A323444 Sum of exponents in prime-power factorization of Product_{k=0..n} binomial(n,k) (A001142).

Original entry on oeis.org

0, 0, 1, 2, 6, 6, 11, 10, 23, 28, 33, 28, 45, 38, 44, 50, 86, 74, 96, 82, 106, 110, 114, 96, 147, 150, 153, 182, 211, 184, 215, 186, 281, 280, 279, 278, 347, 308, 306, 304, 380, 336, 374, 328, 368, 408, 403, 352, 489, 482, 524, 516, 559, 498, 596, 586, 686, 674
Offset: 0

Views

Author

Daniel Suteu, Jan 15 2019

Keywords

Comments

Also sum of exponents in prime-power factorization of hyperfactorial(n) / superfactorial(n).

Examples

			a(4) = 6 because C(4,0)*C(4,1)*C(4,2)*C(4,3)*C(4,4) = 2^5 * 3^1 and 5 + 1 = 6, where C(n,k) is the binomial coefficient.
		

Crossrefs

Programs

  • Mathematica
    Array[Sum[PrimeOmega@ Binomial[#, k], {k, 0, #}] &, 57] (* Michael De Vlieger, Jan 19 2019 *)
  • PARI
    a(n) = sum(k=0, n, bigomega(binomial(n, k)));
    
  • PARI
    a(n) = my(t=0); sum(k=1, n, my(b=bigomega(k)); t+=b; k*b-t);
    
  • PARI
    first(n) = my(res = List([0]), r=0, t=0, b=0); for(k=1, n, b=bigomega(k); t += b; r += k*b-t; listput(res, r)); res \\ adapted from Daniel Suteu \\ David A. Corneth, Jan 16 2019

Formula

a(n) = A303281(n) - A303279(n), for n > 0.
a(n) = A001222(A001142(n)).
Showing 1-9 of 9 results.