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.

A269134 Number of combinatory separations of normal multisets of weight n.

Original entry on oeis.org

1, 4, 14, 57, 223, 948, 3940, 16994, 72964, 317959, 1385592, 6085763, 26738139, 117939291, 520553999, 2301781692, 10181786176, 45074744448, 199558036891, 883670342156, 3912320450786
Offset: 1

Views

Author

Gus Wiseman, Feb 20 2016

Keywords

Comments

A multiset is normal if it spans an initial interval of positive integers. The type of a multiset of integers is the unique normal multiset that has the same sequence of multiplicities when its entries are taken in increasing order. For example the type of 335556 is 112223.
If and only if there exists a multiset partition p whose multiset union has type h and where g = {g_1,...,g_n} is the multiset of types of the blocks of p, there exists a *combinatory separation* which is regarded as a multi-arrow p:h<=g. For example 1122<={12,11} is *not* a combinatory separation because one cannot partition a multiset of type 1122 into two blocks where one block has two distinct elements and the other block has two equal elements. Normal multisets N and combinatory separations S comprise a multi-order (N,S). The value of a(n) is the total number of *distinct* combinatory separations h<=g where h has weight n.
The term "combinatory separation" is inspired by MacMahon's inscrutable "Combinatory Analysis" (1915) which states: "A partition of any number is "separated" into "separates" by writing down a set [sic] of partitions, each partition in its own brackets, from left to right so that when all of the parts of these partitions are assembled in a single bracket, the partition separated is reproduced."

Examples

			For a(3) the 14 distinct combinatory separations grouped according to head are: 111<={111}, 111<={1,11}, 111<={1,1,1}; 112<={112}, 112<={1,11}, 112<={1,12}, 112<={1,1,1}; 122<={122}, 122<={1,11}, 122<={1,12}, 122<={1,1,1}; 123<={123}, 123<={1,12}, 123<={1,1,1}.
Note that in this enumeration the two multiset partitions {{1},{2,3}}:123<={1,12} and {{1,2},{3}}:123<={1,12} do not represent distinct multi-arrows and consequently are counted only once, whereas the two multiset partitions {{1},{1,2}}:112<={1,12} and {{1,2},{2}}:122<={1,12} are counted separately even though they have the same multiset of block-types.
		

Crossrefs

Cf. A255906 (multiset partitions of normal multisets of weight n), A096443 (multiset partitions of multiset class representatives), A007716 (non-isomorphic multiset partitions of weight n).

Programs

  • Mathematica
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];
    allnorm[n_]:=If[n<=0,{{}},Function[s,Array[Count[s,y_/;y<=#]+1&,n]]/@Subsets[Range[n-1]+1]];
    normize[m_]:=m/.Rule@@@Table[{Union[m][[i]],i},{i,Length[Union[m]]}];
    Table[Length[Union@@Table[{m,Sort[normize/@#]}&/@mps[m],{m,allnorm[n]}]],{n,7}] (* Gus Wiseman, Aug 29 2018 *)

Extensions

a(9) from Gus Wiseman, Aug 29 2018
a(10) from Robert Price, Sep 14 2018
a(11)-a(21) from Martin Fuller, Mar 22 2025

A321854 Irregular triangle where T(H(u),H(v)) is the number of ways to partition the Young diagram of u into vertical sections whose sizes are the parts of v, where H is Heinz number.

Original entry on oeis.org

1, 1, 0, 1, 1, 1, 0, 0, 1, 0, 2, 1, 0, 0, 0, 0, 1, 1, 3, 1, 0, 2, 0, 4, 1, 0, 0, 0, 3, 1, 0, 0, 0, 0, 0, 0, 1, 0, 2, 2, 5, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 4, 1, 0, 0, 0, 6, 0, 6, 1, 1, 3, 4, 6, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
Offset: 1

Views

Author

Gus Wiseman, Nov 19 2018

Keywords

Comments

Row n has length A000041(A056239(n)).
A vertical section is a partial Young diagram with at most one square in each row.

Examples

			Triangle begins:
  1
  1
  0  1
  1  1
  0  0  1
  0  2  1
  0  0  0  0  1
  1  3  1
  0  2  0  4  1
  0  0  0  3  1
  0  0  0  0  0  0  1
  0  2  2  5  1
  0  0  0  0  0  0  0  0  0  0  1
  0  0  0  0  0  4  1
  0  0  0  6  0  6  1
  1  3  4  6  1
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  1
  0  0  4 10  4  8  1
The 12th row counts the following partitions of the Young diagram of (211) into vertical sections (shown as colorings by positive integers):
  T(12,7) = 0:
.
  T(12,9) = 2:    1 2   1 2
                  1     2
                  2     1
.
  T(12,10) = 2:   1 2   1 2
                  2     1
                  2     1
.
  T(12,12) = 5:   1 2   1 2   1 2   1 2   1 2
                  3     2     3     1     3
                  3     3     2     3     1
.
  T(12,16) = 1:   1 2
                  3
                  4
		

Crossrefs

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    spsu[,{}]:={{}};spsu[foo,set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@spsu[Select[foo,Complement[#,Complement[set,s]]=={}&],Complement[set,s]]]/@Cases[foo,{i,_}];
    ptnpos[y_]:=Position[Table[1,{#}]&/@y,1];
    ptnverts[y_]:=Select[Rest[Subsets[ptnpos[y]]],UnsameQ@@First/@#&];
    Table[With[{y=Reverse[primeMS[n]]},Table[Length[Select[spsu[ptnverts[y],ptnpos[y]],Sort[Length/@#]==primeMS[k]&]],{k,Sort[Times@@Prime/@#&/@IntegerPartitions[Total[primeMS[n]]]]}]],{n,18}]

A318559 Number of combinatory separations of the multiset of prime factors of n.

Original entry on oeis.org

1, 1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 4, 1, 2, 2, 5, 1, 4, 1, 4, 2, 2, 1, 7, 2, 2, 3, 4, 1, 3, 1, 7, 2, 2, 2, 8, 1, 2, 2, 7, 1, 3, 1, 4, 4, 2, 1, 12, 2, 4, 2, 4, 1, 7, 2, 7, 2, 2, 1, 8, 1, 2, 4, 11, 2, 3, 1, 4, 2, 3, 1, 15, 1, 2, 4, 4, 2, 3, 1, 12, 5, 2, 1, 8, 2, 2
Offset: 1

Views

Author

Gus Wiseman, Aug 28 2018

Keywords

Comments

A multiset is normal if it spans an initial interval of positive integers. The type of a multiset is the unique normal multiset that has the same sequence of multiplicities when its entries are taken in increasing order. For example the type of 335556 is 112223. A (headless) combinatory separation of a multiset m is a multiset of normal multisets {t_1,...,t_k} such that there exist multisets {s_1,...,s_k} with multiset union m and such that s_i has type t_i for each i = 1...k.

Examples

			The a(60) = 8 combinatory separations of {2,2,3,5}:
  {1123},
  {1,112}, {1,123}, {11,12}, {12,12},
  {1,1,11}, {1,1,12},
  {1,1,1,1}.
		

Crossrefs

Programs

  • Mathematica
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    normize[m_]:=m/.Rule@@@Table[{Union[m][[i]],i},{i,Length[Union[m]]}];
    Table[Length[Union[Sort/@Map[normize,mps[primeMS[n]],{2}]]],{n,100}]

A321737 Number of ways to partition the Young diagram of an integer partition of n into vertical sections.

Original entry on oeis.org

1, 1, 3, 9, 37, 152, 780, 3965, 23460, 141471, 944217, 6445643, 48075092, 364921557, 2974423953, 24847873439, 219611194148, 1987556951714, 18930298888792, 184244039718755, 1874490999743203, 19510832177784098, 210941659716920257, 2331530519337226199, 26692555830628617358
Offset: 0

Views

Author

Gus Wiseman, Nov 19 2018

Keywords

Comments

A vertical section is a partial Young diagram with at most one square in each row. For example, a partition (shown as a coloring by positive integers) into vertical sections of the Young diagram of (322) is:
1 2 3
1 2
2 3

Examples

			The a(4) = 37 partitions into vertical sections of integer partitions of 4:
  1 2 3 4
.
  1 2 3   1 2 3   1 2 3   1 2 3
  4       3       2       1
.
  1 2   1 2   1 2   1 2   1 2   1 2   1 2
  3 4   2 3   3 2   1 3   1 2   3 1   2 1
.
  1 2   1 2   1 2   1 2   1 2   1 2   1 2   1 2   1 2   1 2
  3     3     2     3     2     1     1     3     2     1
  4     3     3     2     2     3     2     1     1     1
.
  1   1   1   1   1   1   1   1   1   1   1   1   1   1   1
  2   2   2   2   2   1   1   2   2   2   2   1   1   2   1
  3   3   2   3   2   2   2   1   1   3   2   1   2   1   1
  4   3   3   2   2   3   2   3   2   1   1   2   1   1   1
		

Crossrefs

Programs

  • Mathematica
    spsu[,{}]:={{}};spsu[foo,set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@spsu[Select[foo,Complement[#,Complement[set,s]]=={}&],Complement[set,s]]]/@Cases[foo,{i,_}];
    ptnpos[y_]:=Position[Table[1,{#}]&/@y,1];
    ptnverts[y_]:=Select[Rest[Subsets[ptnpos[y]]],UnsameQ@@First/@#&];
    Table[Sum[Length[spsu[ptnverts[y],ptnpos[y]]],{y,IntegerPartitions[n]}],{n,6}]

Extensions

a(11)-a(24) from Ludovic Schwob, Aug 28 2023

A318562 Number of combinatory separations of strongly normal multisets of weight n with strongly normal parts.

Original entry on oeis.org

1, 4, 10, 32, 80, 239, 605, 1670, 4251
Offset: 1

Views

Author

Gus Wiseman, Aug 29 2018

Keywords

Comments

A multiset is normal if it spans an initial interval of positive integers, and strongly normal if in addition it has weakly decreasing multiplicities. The type of a multiset of integers is the unique normal multiset that has the same sequence of multiplicities when its entries are taken in increasing order. For example the type of 335556 is 112223.
A pair h<={g_1,...,g_k} is a combinatory separation iff there exists a multiset partition of h whose multiset of block-types is {g_1,...,g_k}. For example, the (headless) combinatory separations of the multiset 1122 are {1122}, {1,112}, {1,122}, {11,11}, {12,12}, {1,1,11}, {1,1,12}, {1,1,1,1}. This list excludes {12,11} because one cannot partition 1122 into two blocks where one block has two distinct elements and the other block has two equal elements.

Examples

			The a(3) = 10 combinatory separations:
  111<={111}
  111<={1,11}
  111<={1,1,1}
  112<={112}
  112<={1,11}
  112<={1,12}
  112<={1,1,1}
  123<={123}
  123<={1,12}
  123<={1,1,1}
		

Crossrefs

Programs

  • Mathematica
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];
    strnorm[n_]:=Flatten[MapIndexed[Table[#2,{#1}]&,#]]&/@IntegerPartitions[n];
    normize[m_]:=m/.Rule@@@Table[{Union[m][[i]],i},{i,Length[Union[m]]}];
    strnormQ[m_]:=OrderedQ[Length/@Split[m],GreaterEqual];
    Table[Length[Select[Union@@Table[{m,Sort[normize/@#]}&/@mps[m],{m,strnorm[n]}],And@@strnormQ/@#[[2]]&]],{n,6}]

A318563 Number of combinatory separations of strongly normal multisets of weight n.

Original entry on oeis.org

1, 4, 10, 33, 85, 272, 730, 2197, 6133
Offset: 1

Views

Author

Gus Wiseman, Aug 29 2018

Keywords

Comments

A multiset is normal if it spans an initial interval of positive integers, and strongly normal if in addition it has weakly decreasing multiplicities. The type of a multiset of integers is the unique normal multiset that has the same sequence of multiplicities when its entries are taken in increasing order. For example the type of 335556 is 112223.
A pair h<={g_1,...,g_k} is a combinatory separation iff there exists a multiset partition of h whose multiset of block-types is {g_1,...,g_k}. For example, the (headless) combinatory separations of the multiset 1122 are {1122}, {1,112}, {1,122}, {11,11}, {12,12}, {1,1,11}, {1,1,12}, {1,1,1,1}. This list excludes {12,11} because one cannot partition 1122 into two blocks where one block has two distinct elements and the other block has two equal elements.

Examples

			The a(3) = 10 combinatory separations:
  111<={111}
  111<={1,11}
  111<={1,1,1}
  112<={112}
  112<={1,11}
  112<={1,12}
  112<={1,1,1}
  123<={123}
  123<={1,12}
  123<={1,1,1}
		

Crossrefs

Programs

  • Mathematica
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];
    strnorm[n_]:=Flatten[MapIndexed[Table[#2,{#1}]&,#]]&/@IntegerPartitions[n];
    normize[m_]:=m/.Rule@@@Table[{Union[m][[i]],i},{i,Length[Union[m]]}];
    Table[Length[Union@@Table[{m,Sort[normize/@#]}&/@mps[m],{m,strnorm[n]}]],{n,7}]

A029894 Number of directed (or Gale-Ryser) graphical partitions: degree-vector pairs (in-degree, out-degree) for directed graphs (loops allowed) with n vertices; or possible ordered pair (row-sum, column-sum) vectors for a 0-1 matrix.

Original entry on oeis.org

1, 2, 7, 34, 221, 1736, 15584, 153228, 1611189, 17826202, 205282376, 2441437708, 29816628471, 372314544202, 4737438631001, 61264426341926, 803488037899349, 10668478221202710, 143203795004873285, 1940953294927992976, 26536578116407809962, 365653739580163294032
Offset: 0

Views

Author

torsten.sillke(AT)lhsystems.com

Keywords

References

  • R. A. Brualdi, H. J. Ryser, Combinatorial Matrix Theory, Cambridge Univ. Press, 1992.

Crossrefs

Main diagonal of A327913.

Programs

Formula

Calculated using Cor. 6.3.3, Th. 6.3.6, Cor. 6.2.5 of Brualdi-Ryser.
a(n) = F(n, n, 0, n) where F(b, c, t, w) = Sum_{i=0..b} Sum_{j=ceiling((t+i)/w)..min(t+i, c)} F(i, j, t+i-j, w-1) for w > 0, F(b, c, 0, 0) = 1 and F(b, c, t, 0) = 0 for t > 0. - Andrew Howroyd, Nov 01 2019

Extensions

"Loops allowed" added to the definition by Brendan McKay, Oct 20 2015
a(0)=1 prepended and terms a(12) and beyond from Andrew Howroyd, Oct 31 2019

A318567 Number of pairs (c, y) where c is an integer composition and y is an integer partition and y can be obtained from c by choosing a partition of each part, flattening, and sorting.

Original entry on oeis.org

1, 3, 8, 21, 54, 137, 343, 847, 2075, 5031, 12109, 28921, 68633, 161865, 379655
Offset: 1

Views

Author

Gus Wiseman, Aug 29 2018

Keywords

Comments

Also the number of combinatory separations of normal multisets of weight n with constant parts. A multiset is normal if it spans an initial interval of positive integers. The type of a multiset is the unique normal multiset that has the same sequence of multiplicities when its entries are taken in increasing order. For example the type of 335556 is 112223. A pair h<={g_1,...,g_k} is a combinatory separation iff there exists a multiset partition of h whose multiset of block-types is {g_1,...,g_k}.

Examples

			The a(3) = 8 combinatory separations:
  111<={111}
  111<={1,11}
  111<={1,1,1}
  112<={1,11}
  112<={1,1,1}
  122<={1,11}
  122<={1,1,1}
  123<={1,1,1}
		

Crossrefs

Programs

  • Mathematica
    Table[Sum[Length[Union[Sort/@Join@@@Tuples[IntegerPartitions/@c]]],{c,Join@@Permutations/@IntegerPartitions[n]}],{n,30}]

A327913 Array read by antidiagonals: T(n,m) is the number of distinct unordered row and column sums of n X m binary matrices.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 3, 1, 1, 4, 7, 4, 1, 1, 5, 13, 13, 5, 1, 1, 6, 22, 34, 22, 6, 1, 1, 7, 34, 76, 76, 34, 7, 1, 1, 8, 50, 152, 221, 152, 50, 8, 1, 1, 9, 70, 280, 557, 557, 280, 70, 9, 1, 1, 10, 95, 482, 1264, 1736, 1264, 482, 95, 10, 1, 1, 11, 125, 787, 2630, 4766, 4766, 2630, 787, 125, 11, 1
Offset: 0

Views

Author

Andrew Howroyd, Oct 30 2019

Keywords

Comments

Only matrices in which both row and columns sums are weakly increasing need to be considered. If order is also considered then the number of possibilities is given by A328887(n, m).

Examples

			Array begins:
=============================================
n\m | 0 1  2   3    4     5     6      7
----+----------------------------------------
  0 | 1 1  1   1    1     1     1      1 ...
  1 | 1 2  3   4    5     6     7      8 ...
  2 | 1 3  7  13   22    34    50     70 ...
  3 | 1 4 13  34   76   152   280    482 ...
  4 | 1 5 22  76  221   557  1264   2630 ...
  5 | 1 6 34 152  557  1736  4766  11812 ...
  6 | 1 7 50 280 1264  4766 15584  45356 ...
  7 | 1 8 70 482 2630 11812 45356 153228 ...
  ...
T(2,2) = 7. The following 7 matrices each have different row/column sums.
  [0 0]  [0 0]  [0 1]  [0 0]  [0 1]  [0 1]  [1 1]
  [0 0]  [0 1]  [1 0]  [1 1]  [0 1]  [1 1]  [1 1]
		

Crossrefs

Main diagonal is A029894.
Cf. A028657 (nonequivalent binary n X m matrices).

Programs

  • PARI
    T(n,m)={local(Cache=Map());
      my(F(b, c, t, w)=my(hk=Vecsmall([b, c, t, w]), z);
         if(!mapisdefined(Cache, hk, &z),
           z = if(w&&c, sum(i=0, b, sum(j=ceil((t+i)/w), min(t+i, c), self()(i, j, t+i-j, w-1))), !t);
         mapput(Cache, hk, z)); z);
       F(n, n, 0, m)
    }
    
  • Python
    # After PARI implementation.
    from functools import cache
    @cache
    def F(b, c, t, w):
        if w == 0:
            return 1 if t == 0 else 0
        return sum(
            sum(
                F(i, j, t + i - j, w - 1)
                for j in range((t + i - 1) // w, min(t + i, c) + 1)
            )
            for i in range(b + 1)
        )
    A327913 = lambda n, m: F(n, n, 0, m)
    for n in range(10):
        print([A327913(n, m) for m in range(0, 8)]) # Peter Luschny, Apr 09 2021
Showing 1-9 of 9 results.