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.

A113547 Triangle read by rows: number of labeled partitions of n with maximin m.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 1, 4, 5, 5, 1, 8, 13, 15, 15, 1, 16, 35, 47, 52, 52, 1, 32, 97, 153, 188, 203, 203, 1, 64, 275, 515, 706, 825, 877, 877, 1, 128, 793, 1785, 2744, 3479, 3937, 4140, 4140, 1, 256, 2315, 6347, 11002, 15177, 18313, 20270, 21147, 21147, 1, 512, 6817, 23073, 45368, 68303, 88033, 102678, 111835, 115975, 115975
Offset: 1

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Author

Keywords

Comments

The maximin of a partition is the maximum over all parts of the minimum label in each part. If the rows are reversed, the result is the number of partitions of n with minimax m.
The number of restricted growth functions of length n where the maximum appears first at position m. The RGF's are defined here as f(1)=1 and f(i) <=1+max_{1<=jR. J. Mathar, Mar 18 2016

Examples

			Maximin [123]=max(1)=1, maximin [12|3]=max(1,3)=3, maximin [13|2]=max(1,2)=2, maximin [1|23]=max(1,2)=2 and maximin [1|2|3]=max(1,2,3)=3, so for n=3 the multiset of maximins is {1,2,2,3,3}, making the 3rd line 1,2,2.
1;
1,  1;
1,  2,   2;
1,  4,   5,   5;
1,  8,  13,  15,  15;
1, 16,  35,  47,  52,  52;
1, 32,  97, 153, 188, 203, 203;
1, 64, 275, 515, 706, 825, 877, 877;
		

Crossrefs

A362924 and A362925 are other versions of this triangle. - N. J. A. Sloane, Aug 10 2023

Programs

  • Maple
    A113547 := proc(n,m)
        add(combinat[stirling2](m-1,k-1)*k^(n-m),k=1..m) ;
    end proc:
    seq(seq( A113547(n,m),m=1..n),n=1..10) ; # R. J. Mathar, Mar 13 2016
  • Mathematica
    T[n_, n_] := BellB[n - 1]; T[n_, n_ - 1] := BellB[n - 1]; T[n_, n_ - 2] := BellB[n - 1] - BellB[n - 3]; T[n_, m_] := Sum[StirlingS2[m - 1, k - 1]*k^(n - m), {k, 1, m}]; Table[T[n, m], {n, 1, 5}, {m, 1, n}] (* G. C. Greubel, May 06 2017 *)

Formula

T(n, m) = Sum_{k=1..m} S2(m-1, k-1)*k^(n-m), where S2 is the Stirling numbers of the second kind (A008277). T(n, n)=T(n, n-1)=B(n-1), where B is the Bell numbers (A000110). T(n, n-2)=B(n-1)-B(n-3).
Conjectures: T(n,3) = A007689(n-3). T(n,4) = 2^(n-4)+3^(n-3)+4^(n-4).- R. J. Mathar, Mar 13 2016

A362924 Triangle read by rows: T(n,m), n >= 1, 1 <= m <= n, is number of partitions of the set {1,2,...,n} that have at most one block contained in {1,...,m}.

Original entry on oeis.org

1, 2, 1, 5, 4, 1, 15, 13, 8, 1, 52, 47, 35, 16, 1, 203, 188, 153, 97, 32, 1, 877, 825, 706, 515, 275, 64, 1, 4140, 3937, 3479, 2744, 1785, 793, 128, 1, 21147, 20270, 18313, 15177, 11002, 6347, 2315, 256, 1, 115975, 111835, 102678, 88033, 68303, 45368, 23073, 6817, 512, 1, 678570, 657423, 610989, 536882, 436297, 316305, 191866, 85475, 20195, 1024, 1
Offset: 1

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Author

N. J. A. Sloane, Aug 10 2023, based on an email from Don Knuth

Keywords

Comments

Also, the maximum number of solutions to an exact cover problem with n items, of which m are secondary.

Examples

			Triangle begins:
  [1],
  [2, 1],
  [5, 4, 1],
  [15, 13, 8, 1],
  [52, 47, 35, 16, 1],
  [203, 188, 153, 97, 32, 1],
  [877, 825, 706, 515, 275, 64, 1],
  [4140, 3937, 3479, 2744, 1785, 793, 128, 1],
  [21147, 20270, 18313, 15177, 11002, 6347, 2315, 256, 1],
  [115975, 111835, 102678, 88033, 68303, 45368, 23073, 6817, 512, 1],
  [678570, 657423, 610989, 536882, 436297, 316305, 191866, 85475, 20195, 1024, 1],
...
For example, if n=4, m=3, then T(4,3) = 8, because out of the A000110(4) = 15 set partitions of {1,2,3,4}, those that have 2 or more blocks contained in {1,2,3} are
  {12,3,4},
  {13,2,4},
  {14,2,3},
  {23,1,4},
  {24,1,3},
  {34,1,2},
  {1,2,3,4},
  while
  {1234},
  {123,4},
  {124,3}
  {134,2}
  {234,1},
  {12,34}
  {13. 24}.
  {14, 23}
  do not.
		

References

  • D. E. Knuth, The Art of Computer Programming, Volume 4B, exercise 7.2.2.1--185, answer on page 468.

Crossrefs

See A113547 and A362925 for other versions of this triangle.
Row sums give A005493.

Programs

  • Maple
    with(combinat);
    T:=proc(n,m) local k;
    add(stirling2(n-m,k)*(k+1)^m, k=0..n-m);
    end;
  • Mathematica
    A362924[n_,m_]:=Sum[StirlingS2[n-m,k](k+1)^m,{k,0,n-m}];
    Table[A362924[n,m],{n,15},{m,n}] (* Paolo Xausa, Dec 02 2023 *)

Formula

T(n, 1) = Bell number (all set partitions) A000110(n);
T(n, n) = 1 when m=n (the only possibility is a single block);
T(n, n-1) = 2^{n-1} when m=n-1 (a single block or two blocks);
T(n, 2) = A078468(2).
In general, T(n, m) = Sum_{k=0..n-m} Stirling_2(n-m,k)*(k+1)^m.

A383049 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where A(n,k) is the n-th term of the inverse Stirling transform of j-> (j+1)^k.

Original entry on oeis.org

1, 1, 1, 1, 2, 0, 1, 4, 1, 0, 1, 8, 5, -1, 0, 1, 16, 19, -3, 2, 0, 1, 32, 65, -1, 4, -6, 0, 1, 64, 211, 45, -10, -8, 24, 0, 1, 128, 665, 359, -116, 48, 20, -120, 0, 1, 256, 2059, 2037, -538, 340, -234, -52, 720, 0, 1, 512, 6305, 10079, -1316, 984, -1240, 1302, 72, -5040, 0
Offset: 0

Views

Author

Seiichi Manyama, Apr 14 2025

Keywords

Examples

			Square array begins:
  1,  1,  1,    1,     1,     1,     1, ...
  1,  2,  4,    8,    16,    32,    64, ...
  0,  1,  5,   19,    65,   211,   665, ...
  0, -1, -3,   -1,    45,   359,  2037, ...
  0,  2,  4,  -10,  -116,  -538, -1316, ...
  0, -6, -8,   48,   340,   984, -1148, ...
  0, 24, 20, -234, -1240, -1866, 16400, ...
		

Crossrefs

Columns k=0..6 give A019590(n+1), A302190 (for n > 0), A222627, A222636, A222748, A223023, A383050.
Main diagonal gives A383051.

Programs

  • PARI
    a(n, k) = sum(j=0, n, (j+1)^k*stirling(n, j, 1));

Formula

A(n,k) = Sum_{j=0..n} (j+1)^k * Stirling1(n,j).
E.g.f. of column k: Sum_{j>=0} (j+1)^k * log(1+x)^j / j!.
E.g.f. of column k: (1+x) * Sum_{j=0..k} Stirling2(k+1,j+1) * log(1+x)^j.

A367820 Number of partitions of [2n] that have at most one block contained in [n].

Original entry on oeis.org

1, 2, 13, 153, 2744, 68303, 2224417, 90995838, 4538437039, 269755223485, 18766884323562, 1506040068195721, 137740473851280141, 14212098473767962472, 1640078704487165930485, 210103319793655159244093, 29684467774817808296383256, 4598958815992575305097910699
Offset: 0

Views

Author

Alois P. Heinz, Dec 01 2023

Keywords

Examples

			a(2) = 13: 1234, 123|4, 124|3, 12|34, 12|3|4, 134|2, 13|24, 13|2|4, 14|23, 1|234, 1|23|4, 14|2|3, 1|24|3.
		

Crossrefs

Programs

  • Maple
    b:= proc(n) option remember; expand(`if`(n=0, 1,
          x*add(b(n-j)*binomial(n-1, j-1), j=1..n)))
        end:
    a:= n-> add(coeff(b(n), x, j)*(j+1)^n, j=0..n):
    seq(a(n), n=0..21);
  • Mathematica
    A367820[n_]:=Sum[StirlingS2[n,j](j+1)^n,{j,0,n}];
    Array[A367820,25,0] (* Paolo Xausa, Dec 04 2023 *)

Formula

a(n) = A113547(2n+1,n+1) = A362925(2n,n).
a(n) = Sum_{j=0..n} (j+1)^n * Stirling2(n,j).
a(n) mod 2 = A011655(n+2).

A383052 a(n) = Sum_{k=0..n} (k+1)^3 * Stirling2(n,k).

Original entry on oeis.org

1, 8, 35, 153, 706, 3479, 18313, 102678, 610989, 3844525, 25492752, 177579961, 1295811637, 9879799744, 78525094847, 649253421173, 5573667453498, 49595062947091, 456689512735421, 4345710521536150, 42675672248378721, 431963852263306569, 4501627598926298992
Offset: 0

Views

Author

Seiichi Manyama, Apr 14 2025

Keywords

Comments

Stirling transform of (n+1)^3.

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n, (k+1)^3*stirling(n, k, 2));
    
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, (k+1)^3*(exp(x)-1)^k/k!)))

Formula

a(n) = A362925(n+3,3).
E.g.f.: Sum_{k>=0} (k+1)^3 * (exp(x) - 1)^k / k!.
E.g.f.: exp(exp(x) - 1) * Sum_{k=0..3} Stirling2(4,k+1) * (exp(x) - 1)^k.

A383053 a(n) = Sum_{k=0..n} (k+1)^4 * Stirling2(n,k).

Original entry on oeis.org

1, 16, 97, 515, 2744, 15177, 88033, 536882, 3441439, 23151411, 163135410, 1201594675, 9232595661, 73858810120, 614045917741, 5296398334735, 47321198203496, 437310785441381, 4174403973827181, 41107555809612466, 417122543915965091, 4356601173778017487
Offset: 0

Views

Author

Seiichi Manyama, Apr 14 2025

Keywords

Comments

Stirling transform of (n+1)^4.

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n, (k+1)^4*stirling(n, k, 2));
    
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, (k+1)^4*(exp(x)-1)^k/k!)))

Formula

a(n) = A362925(n+4,4).
E.g.f.: Sum_{k>=0} (k+1)^4 * (exp(x) - 1)^k / k!.
E.g.f.: exp(exp(x) - 1) * Sum_{k=0..4} Stirling2(5,k+1) * (exp(x) - 1)^k.

A383054 a(n) = Sum_{k=0..n} (k+1)^5 * Stirling2(n,k).

Original entry on oeis.org

1, 32, 275, 1785, 11002, 68303, 436297, 2891670, 19947717, 143327725, 1072207680, 8342947657, 67440657877, 565603592392, 4914839764895, 44191989524117, 410644596021954, 3938713285932859, 38950532224469117, 396712750010963782, 4157217331880368521
Offset: 0

Views

Author

Seiichi Manyama, Apr 14 2025

Keywords

Comments

Stirling transform of (n+1)^5.

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n, (k+1)^5*stirling(n, k, 2));
    
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, (k+1)^5*(exp(x)-1)^k/k!)))

Formula

a(n) = A362925(n+5,5).
E.g.f.: Sum_{k>=0} (k+1)^5 * (exp(x) - 1)^k / k!.
E.g.f.: exp(exp(x) - 1) * Sum_{k=0..5} Stirling2(6,k+1) * (exp(x) - 1)^k.
Showing 1-7 of 7 results.