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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A096127 a(n) is the largest k such that (n^2)!/(n!)^k is an integer.

Original entry on oeis.org

3, 4, 5, 6, 8, 8, 9, 10, 12, 12, 14, 14, 16, 18, 17, 18, 20, 20, 22, 24, 24, 24, 26, 26, 28, 28, 30, 30, 32, 32, 33, 35, 36, 38, 38, 38, 40, 42, 42, 42, 44, 44, 46, 48, 48, 48, 50, 50, 52, 54, 55, 54, 56, 58, 58, 60, 60, 60, 62, 62, 64, 66, 65, 67, 68, 68, 70, 72, 73, 72, 74, 74
Offset: 2

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Author

Amarnath Murthy, Jul 03 2004

Keywords

Comments

Conjecture: a(n)=n+1 only when n is prime or a power of a prime. [Verified for n=2..5000. - Amiram Eldar, Apr 06 2021]

Examples

			a(6) = 8 as 36!/(6!)^8 is an integer which is not further divisible by 720.
		

Crossrefs

Programs

  • Mathematica
    f[n_] := Block[{k = n}, While[ IntegerQ[(n^2)!/n!^k], k++ ]; k - 1]; Table[ f[n], {n, 75}] (* Robert G. Wilson v, Jul 03 2004 *)

Extensions

Edited by Don Reble and Robert G. Wilson v, Jul 04 2004

A120666 Triangle read by rows: T(n, k) = (n*k)!/(n!)^k.

Original entry on oeis.org

1, 1, 6, 1, 20, 1680, 1, 70, 34650, 63063000, 1, 252, 756756, 11732745024, 623360743125120, 1, 924, 17153136, 2308743493056, 1370874167589326400, 2670177736637149247308800, 1, 3432, 399072960, 472518347558400, 3177459078523411968000, 85722533226982363751829504000, 7363615666157189603982585462030336000
Offset: 1

Views

Author

Roger L. Bagula, Aug 11 2006

Keywords

Comments

T(m,n) is the number of ways to distribute n*m different toys among m different kids so that each kid gets exactly n toys. For example, with n=3 and m=2, the 6 different toys, t1, t2, t3, t4, t5 and t6, can be distributed in exactly 20 ways among the 2 kids, k1 and k2, since there are C(6,3)=20 ways to choose the three toys for k1, with the other three toys going to k2. The proof for the general case is based on the identity C(n*m,n)*C(n*m-n,n)*...*C(n*m-n*(m-1),n) = (n*m)!/(n!)^m. - Dennis P. Walsh, Apr 12 2018

Examples

			Triangle begins:
  1;
  1,   6;
  1,  20,   1680;
  1,  70,  34650,    63063000;
  1, 252, 756756, 11732745024, 623360743125120;
		

Crossrefs

Programs

  • Magma
    [Factorial(n*k)/(Factorial(n))^k: k in [1..n], n in [1..10]]; // G. C. Greubel, Dec 26 2022
    
  • Maple
    T:= (m, n)-> (n*m)!/(m!)^n:
    seq(seq(T(m, n), n=1..m), m=1..7);  # Alois P. Heinz, Apr 12 2018
  • Mathematica
    Table[(n*k)!/(n!)^k, {n,10}, {k,n}]//Flatten
  • SageMath
    def A120666(n,k): return gamma(n*k+1)/(factorial(n))^k
    flatten([[A120666(n,k) for k in range(1,n+1)] for n in range(1,11)]) # G. C. Greubel, Dec 26 2022

Formula

T(n, k) = (k*n)!/(n!)^k.

Extensions

Edited by N. J. A. Sloane, Jun 17 2007
Offset corrected by Alois P. Heinz, Apr 12 2018
New name using formula by Joerg Arndt, Apr 15 2018

A141906 Triangle t(n,m) = (n*m)!/(m!^n) read by rows, 0<=m<=n.

Original entry on oeis.org

1, 1, 1, 1, 2, 6, 1, 6, 90, 1680, 1, 24, 2520, 369600, 63063000, 1, 120, 113400, 168168000, 305540235000, 623360743125120, 1, 720, 7484400, 137225088000, 3246670537110000, 88832646059788350720, 2670177736637149247308800
Offset: 0

Views

Author

Roger L. Bagula and Gary W. Adamson, Sep 14 2008

Keywords

Comments

Row sums are in A221177.

Examples

			1;
1, 1;
1, 2, 6;
1, 6, 90, 1680;
1, 24, 2520, 369600, 63063000;
1, 120, 113400, 168168000, 305540235000, 623360743125120;
1, 720, 7484400, 137225088000, 3246670537110000, 88832646059788350720, 2670177736637149247308800;
		

Crossrefs

Programs

  • Maple
    A141906 := proc(n,m)
            (n*m)!/m!^n ;
    end proc:
    seq(seq(A141906(n,m),m=0..n),n=0..5) ; # R. J. Mathar, Nov 08 2011
  • Mathematica
    Clear[t, n, m]; t[n_, m_] = (n*m)!/m!^n; Table[Table[t[n, m], {m, 0, n}], {n, 0, 10}]; Flatten[%]

A268751 Number of sequences with n copies each of 1,2,...,n avoiding the pattern 12...n.

Original entry on oeis.org

0, 0, 1, 374, 16140983, 173996758190594, 791857392420720220446647, 2285085934263252199073238394141449534, 5841526335200139692050292842849347521755651331941759, 17585875137049122003330684747231440185032966840579881629527695901745706
Offset: 0

Views

Author

Alois P. Heinz, Feb 12 2016

Keywords

Examples

			a(2) = 1: 2211.
a(3) = 374: 111333222, 113133222, 113313222, ..., 333221121, 333221211, 333222111.
		

Crossrefs

Main diagonal of A269129.

Formula

a(n) = A034841(n) - A268485(n).

A340590 Number of n*(n+1)-step n-dimensional nonnegative closed lattice walks starting at the origin and using steps that increment all components or decrement one component by 1.

Original entry on oeis.org

1, 1, 16, 24444, 8204167296, 1052109889288796160, 78607706455594117933558272000, 4825997038234002956322487606996722432307200, 325844502690869718672482402463320899403011435565608069632000, 31176247959648026790291638390172796940342899651173947284143811081979726010777600
Offset: 0

Views

Author

Alois P. Heinz, Jan 12 2021

Keywords

Examples

			a(2) = 16:
  [(0,0),(1,1),(0,1),(0,0),(1,1),(0,1),(0,0)],
  [(0,0),(1,1),(0,1),(0,0),(1,1),(1,0),(0,0)],
  [(0,0),(1,1),(0,1),(1,2),(0,2),(0,1),(0,0)],
  [(0,0),(1,1),(0,1),(1,2),(1,1),(0,1),(0,0)],
  [(0,0),(1,1),(0,1),(1,2),(1,1),(1,0),(0,0)],
  [(0,0),(1,1),(1,0),(0,0),(1,1),(0,1),(0,0)],
  [(0,0),(1,1),(1,0),(0,0),(1,1),(1,0),(0,0)],
  [(0,0),(1,1),(1,0),(2,1),(1,1),(0,1),(0,0)],
  [(0,0),(1,1),(1,0),(2,1),(1,1),(1,0),(0,0)],
  [(0,0),(1,1),(1,0),(2,1),(2,0),(1,0),(0,0)],
  [(0,0),(1,1),(2,2),(1,2),(0,2),(0,1),(0,0)],
  [(0,0),(1,1),(2,2),(1,2),(1,1),(0,1),(0,0)],
  [(0,0),(1,1),(2,2),(1,2),(1,1),(1,0),(0,0)],
  [(0,0),(1,1),(2,2),(2,1),(1,1),(0,1),(0,0)],
  [(0,0),(1,1),(2,2),(2,1),(1,1),(1,0),(0,0)],
  [(0,0),(1,1),(2,2),(2,1),(2,0),(1,0),(0,0)].
		

Crossrefs

Main diagonal of A340591.

Programs

  • Maple
    b:= proc(n, l) option remember; `if`(n=0, 1, (k-> add(
         `if`(l[i]>0, b(n-1, sort(subsop(i=l[i]-1, l))), 0), i=1..k)+
         `if`(add(i, i=l)+k x+1, l)), 0))(nops(l)))
        end:
    a:= n-> b(n*(n+1), [0$n]):
    seq(a(n), n=0..9);
  • Mathematica
    b[n_, l_] := b[n, l] = If[n == 0, 1, Function[k, Sum[
        If[l[[i]]>0, b[n-1, Sort[ReplacePart[l, i -> l[[i]]-1]]], 0], {i, 1, k}] +
        If[Sum[i, {i, l}] + k < n, b[n - 1, Map[#+1&, l]], 0]][Length[l]]];
    a[n_] := b[n(n+1), Table[0, {n}]];
    a /@ Range[0, 9] (* Jean-François Alcover, Jan 26 2021, after Alois P. Heinz *)

Formula

a(n) = A340591(n,n).

A345466 a(n) = Product_{k=1..n} binomial(n, floor(n/k)).

Original entry on oeis.org

1, 1, 2, 9, 96, 1250, 64800, 1764735, 224788480, 22499086176, 6123600000000, 408514437465750, 1308805762115174400, 133962125607455951520, 99335199198879310098432, 113040832521732593994140625, 425230288403106927476736000000, 72623663171934137824096600064000
Offset: 0

Views

Author

Vaclav Kotesovec, Jun 20 2021

Keywords

Crossrefs

Programs

  • Magma
    [n eq 0 select 1 else (&*[Binomial(n,Floor(n/j)): j in [1..n]]): n in [0..30]]; // G. C. Greubel, Feb 05 2024
    
  • Mathematica
    Table[Product[Binomial[n, Floor[n/k]], {k, 1, n}], {n, 0, 20}]
    Table[Product[((n + 1)/k - 1)^Floor[n/k], {k, 1, n}], {n, 0, 20}] (* Vaclav Kotesovec, Jun 24 2021 *)
  • SageMath
    [product(binomial(n,(n//j)) for j in range(1,n+1)) for n in range(31)] # G. C. Greubel, Feb 05 2024

Formula

log(a(n)) ~ n * log(n)^2 / 2. - Vaclav Kotesovec, Jun 21 2021
a(n) = Product_{k=1..n} ((n+1)/k - 1)^floor(n/k). - Vaclav Kotesovec, Jun 24 2021

A375693 Number of multiset permutations of {{1}^n, {2}^n, ..., {n}^n} with no fixed n-tuple {j}^n.

Original entry on oeis.org

1, 0, 5, 1622, 62924817, 623302086965044, 2670169511426774520697375, 7363615066099523741730150062678073534, 18165723898797467057177720588121375861340650728031233, 53130688704554689391452744667655289291011354800478739192999936981375688
Offset: 0

Views

Author

Alois P. Heinz, Aug 24 2024

Keywords

Examples

			a(2) = 5: 1212, 1221, 2112, 2121, 2211.
		

Crossrefs

Main diagonal of A375694.

Programs

  • Maple
    a:= n-> add((-1)^(n-j)*binomial(n, j)*(n*j)!/n!^j, j=0..n):
    seq(a(n), n=0..10);

Formula

a(n) = Sum_{j=0..n} (-1)^(n-j)*binomial(n,j)*(n*j)!/n!^j.
a(n) mod 2 = 1 - (n mod 2) = A059841(n).

A378382 Number of maximal chains in the poset of all binary words of length <= n, ordered by B covers A iff A_i <= B_{i+k} for all i in A and some k >= 0.

Original entry on oeis.org

1, 1, 2, 5, 16, 57, 226, 961, 4376, 21041, 106534, 563961, 3112924, 17839993, 105907946, 649432673, 4105783696, 26706965985, 178466243662, 1223248786921, 8589272300516, 61708802126441, 453143009601682, 3397715981566545, 25990997059282456, 202666687407866257
Offset: 0

Views

Author

John Tyler Rascoe, Nov 26 2024

Keywords

Examples

			a(3) = 5:
 () < (0) < (0,0) < (0,0,0),
 () < (0) < (0,0) < (0,1),
 () < (0) < (0,0) < (1,0),
 () < (0) < (1) < (0,1),
 () < (0) < (1) < (1,0).
		

Crossrefs

Cf. A034841, A143672, A282698, A317145, column k=2 of A378588, A378608.

Programs

  • Python
    def mchains(n, k): return # See A378588
    def A378382_list(max_n): return mchains(max_n,2)

A229051 G.f.: Sum_{n>=0} (n^2)!/n!^n * (2*x)^n / (1-x)^(n^2+1).

Original entry on oeis.org

1, 3, 29, 13567, 1009142769, 19947560933879891, 170891375663413844489045533, 942542805274443250197129297402029958879, 4650425326497533656923054675764068523027405525255181377, 27202912617670436035808496756146798219927348043651854025145948950565355779
Offset: 0

Views

Author

Paul D. Hanna, Sep 22 2013

Keywords

Examples

			G.f.: A(x) = 1 + 3*x + 29*x^2 + 13567*x^3 + 1009142769*x^4 +...
where
A(x) = 1/(1-x) + (2*x)/(1-x)^2 + (4!/2!^2)*(2*x)^2/(1-x)^5 + (9!/3!^3)*(2*x)^3/(1-x)^10 + (16!/4!^4)*(2*x)^4/(1-x)^17 + (25!/5!^5)*(2*x)^5/(1-x)^26 +...
Equivalently,
A(x) = 1/(1-x) + (2*x)/(1-x)^2 + 6*(2*x)^2/(1-x)^5 + 1680*(2*x)^3/(1-x)^10 + 63063000*(2*x)^4/(1-x)^17 + 623360743125120*(2*x)^5/(1-x)^26 +...+ A034841(n)*(2*x)^n/(1-x)^(n^2+1) +...
Illustrate formula a(n) = Sum_{k=0..n} 2^k * Product_{j=0..k-1} C(n+j*k,k) for initial terms:
a(0) = 1;
a(1) = 1 + 2*C(1,1);
a(2) = 1 + 2*C(2,1) + 4*C(2,2)*C(4,2);
a(3) = 1 + 2*C(3,1) + 4*C(3,2)*C(5,2) + 8*C(3,3)*C(6,3)*C(9,3);
a(4) = 1 + 2*C(4,1) + 4*C(4,2)*C(6,2) + 8*C(4,3)*C(7,3)*C(10,3) + 16*C(4,4)*C(8,4)*C(12,4)*C(16,4);
a(5) = 1 + 2*C(5,1) + 4*C(5,2)*C(7,2) + 8*C(5,3)*C(8,3)*C(11,3) + 16*C(5,4)*C(9,4)*C(13,4)*C(17,4) + 32*C(5,5)*C(10,5)*C(15,5)*C(20,5)*C(25,5); ...
which numerically equals:
a(0) = 1;
a(1) = 1 + 2*1 = 3;
a(2) = 1 + 2*2 + 4*1*6 = 29;
a(3) = 1 + 2*3 + 4*3*10 + 8*1*20*84 = 13567;
a(4) = 1 + 2*4 + 4*6*15 + 8*4*35*120 + 16*1*70*495*1820 = 1009142769;
a(5) = 1 + 2*5 + 4*10*21 + 8*10*56*165 + 16*5*126*715*2380 + 32*1*252*3003*15504*53130 = 19947560933879891; ...
		

Crossrefs

Programs

  • Maple
    with(combinat):
    a:= n-> add(2^k*multinomial(n+(k-1)*k, n-k, k$k), k=0..n):
    seq(a(n), n=0..10);  # Alois P. Heinz, Sep 23 2013
  • Mathematica
    Table[Sum[2^k*Product[Binomial[n+j*k,k],{j,0,k-1}],{k,0,n}],{n,0,10}] (* Vaclav Kotesovec, Sep 23 2013 *)
  • PARI
    {a(n)=polcoeff(sum(m=0, n, (m^2)!/m!^m*(2*x)^m/(1-x+x*O(x^n))^(m^2+1)), n)}
    for(n=0,15,print1(a(n),", "))
    
  • PARI
    {a(n)=sum(k=0,n,2^k*prod(j=0,k-1,binomial(n+j*k,k)))}
    for(n=0,15,print1(a(n),", "))

Formula

a(n) = Sum_{k=0..n} 2^k * Product_{j=0..k-1} binomial(n+j*k,k).
a(n) ~ exp(-1/12) * n^(n^2-n/2+1) * 2^n / (2*Pi)^((n-1)/2). - Vaclav Kotesovec, Sep 23 2013

A306241 a(n) = Sum_{k=0..n} (k*n)!/n!^k.

Original entry on oeis.org

1, 2, 8, 1702, 63097722, 623372476627154, 2670179107513625597282318, 7363615751879726008424500256018442794, 18165723935734974232438957032838329596079311234990642
Offset: 0

Views

Author

Seiichi Manyama, Jan 31 2019

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[(k*n)!/n!^k,{k,0,n}],{n,0,10}] (* Vaclav Kotesovec, Feb 08 2019 *)
  • PARI
    {a(n) = sum(k=0, n, (k*n)!/n!^k)}

Formula

a(n) equals (row sums of A120666) + 1.
From Vaclav Kotesovec, Feb 08 2019: (Start)
a(n) ~ A034841(n).
a(n) ~ n^(n^2 - n/2 + 1) / (exp(1/12) * (2*Pi)^((n-1)/2)). (End)
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