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 1-10 of 14 results. Next

A005651 Sum of multinomial coefficients (n_1+n_2+...)!/(n_1!*n_2!*...) where (n_1, n_2, ...) runs over all integer partitions of n.

Original entry on oeis.org

1, 1, 3, 10, 47, 246, 1602, 11481, 95503, 871030, 8879558, 98329551, 1191578522, 15543026747, 218668538441, 3285749117475, 52700813279423, 896697825211142, 16160442591627990, 307183340680888755, 6147451460222703502, 129125045333789172825, 2841626597871149750951
Offset: 0

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Author

Keywords

Comments

This is the total number of hierarchies of n labeled elements arranged on 1 to n levels. A distribution of elements onto levels is "hierarchical" if a level l+1 contains <= elements than level l. Thus for n=4 the arrangement {1,2}:{3}{4} is not allowed. See also A140585. Examples: Let the colon ":" separate two consecutive levels l and l+1. Then n=2 --> 3: {1}{2}, {1}:{2}, {2}:{1}, n=3 --> 10: {1}{2}{3}, {1}{2}:{3}, {3}{1}:{2}, {2}{3}:{1}, {1}:{2}:{3}, {3}:{1}:{2}, {2}:{3}:{1}, {1}:{3}:{2}, {2}:{1}:{3}, {3}:{2}:{1}. - Thomas Wieder, May 17 2008
n identical objects are painted by dipping them into a long row of cans of paint of distinct colors. Begining with the first can and not skipping any cans k, 1<=k<=n, objects are dipped (painted) and not more objects are dipped into any subsequent can than were dipped into the previous can. The painted objects are then linearly ordered. - Geoffrey Critzer, Jun 08 2009
a(n) is the number of partitions of n where each part i is marked with a word of length i over an n-ary alphabet whose letters appear in alphabetical order and all n letters occur exactly once in the partition. a(3) = 10: 3abc, 2ab1c, 2ac1b, 2bc1a, 1a1b1c, 1a1c1b, 1b1a1c, 1b1c1a, 1c1a1b, 1c1b1a. - Alois P. Heinz, Aug 30 2015
Also the number of ordered set partitions of {1,...,n} with weakly decreasing block sizes. - Gus Wiseman, Sep 03 2018
The parity of a(n) is that of A000110(A000120(n)), so a(n) is even if and only if A000120(n) == 2 (mod 3). - Álvar Ibeas, Aug 11 2020

Examples

			For n=3, say the first three cans in the row contain red, white, and blue paint respectively. The objects can be painted r,r,r or r,r,w or r,w,b and then linearly ordered in 1 + 3 + 6 = 10 ways. - _Geoffrey Critzer_, Jun 08 2009
From _Gus Wiseman_, Sep 03 2018: (Start)
The a(3) = 10 ordered set partitions with weakly decreasing block sizes:
  {{1},{2},{3}}
  {{1},{3},{2}}
  {{2},{1},{3}}
  {{2},{3},{1}}
  {{3},{1},{2}}
  {{3},{2},{1}}
  {{2,3},{1}}
  {{1,2},{3}}
  {{1,3},{2}}
  {{1,2,3}}
(End)
		

References

  • Abramowitz and Stegun, Handbook, p. 831, column labeled "M_1".
  • L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 126.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Main diagonal of: A226873, A261719, A309973.
Row sums of: A226874, A262071, A327803.
Column k=1 of A309951.
Column k=0 of A327801.

Programs

  • Maple
    A005651b := proc(k) add( d/(d!)^(k/d),d=numtheory[divisors](k)) ; end proc:
    A005651 := proc(n) option remember; local k ; if n <= 1 then 1; else (n-1)!*add(A005651b(k)*procname(n-k)/(n-k)!, k=1..n) ; end if; end proc:
    seq(A005651(k), k=0..10) ; # R. J. Mathar, Jan 03 2011
    # second Maple program:
    b:= proc(n, i) option remember; `if`(n=0 or i=1, n!,
          b(n, i-1) +binomial(n, i)*b(n-i, min(n-i, i)))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..25);  # Alois P. Heinz, Aug 29 2015, Dec 12 2016
  • Mathematica
    Table[Total[n!/Map[Function[n, Apply[Times, n! ]], IntegerPartitions[n]]], {n, 0, 20}] (* Geoffrey Critzer, Jun 08 2009 *)
    Table[Total[Apply[Multinomial, IntegerPartitions[n], {1}]], {n, 0, 20}] (* Jean-François Alcover and Olivier Gérard, Sep 11 2014 *)
    b[n_, i_, t_] := b[n, i, t] = If[t==1, 1/n!, Sum[b[n-j, j, t-1]/j!, {j, i, n/t}]]; a[n_] := If[n==0, 1, n!*b[n, 0, n]]; Table[a[n], {n, 0, 25}] (* Jean-François Alcover, Nov 20 2015, after Alois P. Heinz *)
  • Maxima
    a(m,n):=if n=m then 1 else sum(binomial(n,k)*a(k,n-k),k,m,(n/2))+1;
    makelist(a(1,n),n,0,17); /* Vladimir Kruchinin, Sep 06 2014 */
    
  • PARI
    a(n)=my(N=n!,s);forpart(x=n,s+=N/prod(i=1,#x,x[i]!));s \\ Charles R Greathouse IV, May 01 2015
    
  • PARI
    { my(n=25); Vec(serlaplace(prod(k=1, n, 1/(1-x^k/k!) + O(x*x^n)))) } \\ Andrew Howroyd, Dec 20 2017

Formula

E.g.f.: 1 / Product (1 - x^k/k!).
a(n) = Sum_{k=1..n} (n-1)!/(n-k)!*b(k)*a(n-k), where b(k) = Sum_{d divides k} d*d!^(-k/d). - Vladeta Jovovic, Oct 14 2002
a(n) ~ c * n!, where c = Product_{k>=2} 1/(1-1/k!) = A247551 = 2.52947747207915264... . - Vaclav Kotesovec, May 09 2014
a(n) = S(n,1), where S(n,m) = sum(k=m..n/2 , binomial(n,k)*S(n-k,k))+1, S(n,n)=1, S(n,m)=0 for nVladimir Kruchinin, Sep 06 2014
E.g.f.: exp(Sum_{k>=1} Sum_{j>=1} x^(j*k)/(k*(j!)^k)). - Ilya Gutkovskiy, Jun 18 2018

Extensions

More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 29 2003

A262072 Number T(n,k) of partitions of an n-set with distinct block sizes and maximal block size equal to k; triangle T(n,k), n>=0, ceiling((sqrt(1+8*n)-1)/2)<=k<=n, read by rows.

Original entry on oeis.org

1, 1, 1, 3, 1, 4, 1, 10, 5, 1, 60, 15, 6, 1, 140, 21, 7, 1, 280, 224, 28, 8, 1, 1260, 630, 336, 36, 9, 1, 12600, 3780, 1050, 480, 45, 10, 1, 34650, 7392, 1650, 660, 55, 11, 1, 110880, 74844, 12672, 2475, 880, 66, 12, 1, 360360, 276276, 140712, 20592, 3575, 1144, 78, 13, 1
Offset: 0

Views

Author

Alois P. Heinz, Sep 10 2015

Keywords

Examples

			Triangle T(n,k) begins:
: 1;
:    1;
:       1;
:       3,  1;
:           4,     1;
:          10,     5,    1;
:          60,    15,    6,    1;
:                140,   21,    7,   1;
:                280,  224,   28,   8,  1;
:               1260,  630,  336,  36,  9,  1;
:              12600, 3780, 1050, 480, 45, 10, 1;
		

Crossrefs

Row sums give A007837.
Column sums give A262073.
Cf. A002024, A262071, A262078 (same read by columns).

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(i*(i+1)/2n, 0, binomial(n, i)*b(n-i, i-1))))
        end:
    T:= (n, k)-> b(n, k) -`if`(k=0, 0, b(n, k-1)):
    seq(seq(T(n,k), k=ceil((sqrt(1+8*n)-1)/2)..n), n=0..14);
  • Mathematica
    b[n_, i_] := b[n, i] = If[i*(i+1)/2n, 0, Binomial[n, i]*b[n-i, i-1]]]]; T[n_, k_] := b[n, k] - If[k == 0, 0, b[n, k-1]]; Table[T[n, k], {n, 0, 14}, {k, Ceiling[(Sqrt[1+8*n]-1)/2], n}] // Flatten (* Jean-François Alcover, Feb 04 2017, translated from Maple *)

A262078 Number T(n,k) of partitions of an n-set with distinct block sizes and maximal block size equal to k; triangle T(n,k), k>=0, k<=n<=k*(k+1)/2, read by columns.

Original entry on oeis.org

1, 1, 1, 3, 1, 4, 10, 60, 1, 5, 15, 140, 280, 1260, 12600, 1, 6, 21, 224, 630, 3780, 34650, 110880, 360360, 2522520, 37837800, 1, 7, 28, 336, 1050, 7392, 74844, 276276, 1513512, 9459450, 131171040, 428828400, 2058376320, 9777287520, 97772875200, 2053230379200
Offset: 0

Views

Author

Alois P. Heinz, Sep 10 2015

Keywords

Examples

			Triangle T(n,k) begins:
: 1;
:    1;
:       1;
:       3,  1;
:           4,     1;
:          10,     5,    1;
:          60,    15,    6,    1;
:                140,   21,    7,   1;
:                280,  224,   28,   8,  1;
:               1260,  630,  336,  36,  9,  1;
:              12600, 3780, 1050, 480, 45, 10, 1;
		

Crossrefs

Row sums give A007837.
Column sums give A262073.
Cf. A000217, A002024, A262071, A262072 (same read by rows).

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(i*(i+1)/2n, 0, binomial(n, i)*b(n-i, i-1))))
        end:
    T:= (n, k)-> b(n, k) -`if`(k=0, 0, b(n, k-1)):
    seq(seq(T(n, k), n=k..k*(k+1)/2), k=0..7);
  • Mathematica
    b[n_, i_] := b[n, i] = If[i*(i+1)/2n, 0, Binomial[n, i]*b[n-i, i-1]]]]; T[n_, k_] :=  b[n, k] - If[k==0, 0, b[n, k-1]]; Table[T[n, k], {k, 0, 7}, {n, k, k*(k+1)/2}] // Flatten (* Jean-François Alcover, Dec 18 2016, after Alois P. Heinz *)

A266518 Number of ordered partitions of a 2n-set with nondecreasing block sizes and maximal block size equal to n.

Original entry on oeis.org

1, 2, 18, 200, 3290, 61992, 1480248, 39402792, 1229123610, 42349478600, 1640551617848, 69364811821032, 3222214209737432, 161656803984848200, 8772238289222220600, 509677254444910662000, 31677425399312755814970, 2092539622373193784503240
Offset: 0

Views

Author

Alois P. Heinz, Dec 30 2015

Keywords

Crossrefs

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
           b(n, i-1)+`if`(i>n, 0, binomial(n, i)*b(n-i, i))))
        end:
    a:= n-> `if`(n=0, 1, b(2*n, n)-b(2*n, n-1)):
    seq(a(n), n=0..20);
  • Mathematica
    b[n_, i_] := b[n, i] = If[n==0, 1, If[i<1, 0, b[n, i-1] + If[i>n, 0, Binomial[n, i]*b[n-i, i]]]]; a[n_] := If[n==0, 1, b[2n, n] - b[2n, n-1]]; Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Feb 27 2017, translated from Maple *)

Formula

a(n) = (2n)! * [x^n] Product_{i=1..n} (i-1)!/(i!-x^i).
a(n) = A262071(2n,n).
a(n) ~ c * 2^(2*n+1/2) * n^n / exp(n), where c = A247551 = 2.529477472079152648... . - Vaclav Kotesovec, Jan 02 2016
a(n) = A327801(2n,n). - Alois P. Heinz, Sep 26 2019

A272492 Number of ordered set partitions of [n] with nondecreasing block sizes and maximal block size equal to two.

Original entry on oeis.org

1, 3, 18, 90, 630, 4410, 37800, 340200, 3515400, 38669400, 471517200, 6129723600, 86497210800, 1297458162000, 20841060240000, 354298024080000, 6389869069584000, 121407512322096000, 2430526127309280000, 51041048673494880000, 1123451899297247520000
Offset: 2

Views

Author

Alois P. Heinz, May 01 2016

Keywords

Crossrefs

Column k=2 of A262071.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
           b(n, i-1)+`if`(i>n, 0, binomial(n, i)*b(n-i, i))))
        end:
    a:= n-> (k-> b(n, k) -b(n, k-1))(2):
    seq(a(n), n=2..30);
  • Mathematica
    Table[n!*(1 + ((-1)^n*(Sqrt[2] - 1) - Sqrt[2] - 1)/2^(n/2 + 1)), {n, 2, 20}] (* Vaclav Kotesovec, May 07 2016 *)

Formula

E.g.f.: x^2 * Product_{i=1..2} (i-1)!/(i!-x^i).
Recurrence: 2*a(n) = 2*n*a(n-1) + (n-1)*n*a(n-2) - (n-2)*(n-1)*n*a(n-3). - Vaclav Kotesovec, May 07 2016

A272493 Number of ordered set partitions of [n] with nondecreasing block sizes and maximal block size equal to three.

Original entry on oeis.org

1, 4, 30, 200, 1610, 13440, 130200, 1327200, 15107400, 183321600, 2422820400, 34104470400, 515897382000, 8276556288000, 141290381232000, 2546760408192000, 48489153817104000, 970454450085120000, 20400874234060320000, 448974320483969280000
Offset: 3

Views

Author

Alois P. Heinz, May 01 2016

Keywords

Crossrefs

Column k=3 of A262071.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
           b(n, i-1)+`if`(i>n, 0, binomial(n, i)*b(n-i, i))))
        end:
    a:= n-> (k-> b(n, k) -b(n, k-1))(3):
    seq(a(n), n=3..30);
  • Mathematica
    FullSimplify[Table[n! * ((-35*(1 + Sqrt[2]) + 7*2^(1 + n/2)* (3*Sqrt[2] - 2) - 5*(-1)^n*(17*Sqrt[2] - 23))/2^(n/2) + 2^(5/6 - n/3)* 3^(-1 - n/3)*((11*3^(1/3) + 6*2^(1/3)* 3^(2/3))*(3 - Sqrt[2]) + 13*2^(1/6)*(3*Sqrt[2] - 2) + (26*2^(1/6)*(3*Sqrt[2] - 2) - (11*3^(1/3) + 6*2^(1/3)*3^(2/3))* (3 - Sqrt[2]))*Cos[2*n*Pi/3] + 3^(1/6)*(3 - Sqrt[2])*(11*3^(2/3) - 18*2^(1/3))*Sin[2*n*Pi/3])) / (35*(3*Sqrt[2] - 2)), {n, 3, 20}]] (* Vaclav Kotesovec, May 07 2016 *)

Formula

E.g.f.: x^3 * Product_{i=1..3} (i-1)!/(i!-x^i).
Recurrence: 12*a(n) = 12*n*a(n-1) + 6*(n-1)*n*a(n-2) - 4*(n-2)*(n-1)*n*a(n-3) - 2*(n-3)*(n-2)*(n-1)*n*a(n-4) - (n-4)*(n-3)*(n-2)*(n-1)*n*a(n-5) + (n-5)*(n-4)*(n-3)*(n-2)*(n-1)*n*a(n-6). - Vaclav Kotesovec, May 07 2016

A272494 Number of ordered set partitions of [n] with nondecreasing block sizes and maximal block size equal to four.

Original entry on oeis.org

1, 5, 45, 350, 3290, 30870, 334950, 3765300, 46950750, 617867250, 8815156350, 133031398500, 2149039893000, 36645888279000, 662781093975000, 12612741639498000, 252857867367105000, 5314211504296695000, 117053051989758885000, 2693288170000578150000
Offset: 4

Views

Author

Alois P. Heinz, May 01 2016

Keywords

Crossrefs

Column k=4 of A262071.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
           b(n, i-1)+`if`(i>n, 0, binomial(n, i)*b(n-i, i))))
        end:
    a:= n-> (k-> b(n, k) -b(n, k-1))(4):
    seq(a(n), n=4..30);
  • Mathematica
    b[n_, i_] := b[n, i] = If[n == 0, 1, If[i < 1, 0, b[n, i - 1] + If[i > n, 0, Binomial[n, i]*b[n - i, i]]]];
    a[n_] := b[n, 4] - b[n, 3];
    a /@ Range[4, 30] (* Jean-François Alcover, Dec 11 2020, after Alois P. Heinz *)

Formula

E.g.f.: x^4 * Product_{i=1..4} (i-1)!/(i!-x^i).

A272495 Number of ordered set partitions of [n] with nondecreasing block sizes and maximal block size equal to five.

Original entry on oeis.org

1, 6, 63, 560, 5922, 61992, 739662, 9086616, 122792670, 1741884144, 26631631026, 428931318816, 7362963616008, 132977285400960, 2538822785931432, 50863863365419104, 1070731366348427784, 23576426902769412672, 542918591829347774040, 13035693339696004705728
Offset: 5

Views

Author

Alois P. Heinz, May 01 2016

Keywords

Crossrefs

Column k=5 of A262071.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
           b(n, i-1)+`if`(i>n, 0, binomial(n, i)*b(n-i, i))))
        end:
    a:= n-> (k-> b(n, k) -b(n, k-1))(5):
    seq(a(n), n=5..30);
  • Mathematica
    b[n_, i_] := b[n, i] = If[n == 0, 1, If[i < 1, 0, b[n, i - 1] + If[i > n, 0, Binomial[n, i]*b[n - i, i]]]];
    a[n_] := b[n, 5] - b[n, 4];
    a /@ Range[5, 30] (* Jean-François Alcover, Dec 11 2020, after Alois P. Heinz *)

Formula

E.g.f.: x^5 * Product_{i=1..5} (i-1)!/(i!-x^i).

A272496 Number of ordered set partitions of [n] with nondecreasing block sizes and maximal block size equal to six.

Original entry on oeis.org

1, 7, 84, 840, 9870, 113652, 1480248, 19699680, 286768482, 4358914560, 71096721696, 1216711960464, 22116370171896, 421629228820800, 8473857766133760, 178260053918650704, 3931319749640138856, 90499126549555707984, 2174651142277047610176, 54390059451824183287200
Offset: 6

Views

Author

Alois P. Heinz, May 01 2016

Keywords

Crossrefs

Column k=6 of A262071.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
           b(n, i-1)+`if`(i>n, 0, binomial(n, i)*b(n-i, i))))
        end:
    a:= n-> (k-> b(n, k) -b(n, k-1))(6):
    seq(a(n), n=6..30);

Formula

E.g.f.: x^6 * Product_{i=1..6} (i-1)!/(i!-x^i).

A272497 Number of ordered set partitions of [n] with nondecreasing block sizes and maximal block size equal to seven.

Original entry on oeis.org

1, 8, 108, 1200, 15510, 194832, 2749032, 39402792, 614555370, 9964468800, 172686804576, 3129181488576, 60039964804248, 1204868044448640, 25426155055055040, 560350692475352064, 12919636322380914984, 310342487192287684992, 7768115419959585662400
Offset: 7

Views

Author

Alois P. Heinz, May 01 2016

Keywords

Crossrefs

Column k=7 of A262071.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
           b(n, i-1)+`if`(i>n, 0, binomial(n, i)*b(n-i, i))))
        end:
    a:= n-> (k-> b(n, k) -b(n, k-1))(7):
    seq(a(n), n=7..30);

Formula

E.g.f.: x^7 * Product_{i=1..7} (i-1)!/(i!-x^i).
Showing 1-10 of 14 results. Next