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 1-6 of 6 results.

A356939 MM-numbers of multisets of intervals. Products of primes indexed by members of A073485.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 20, 22, 24, 25, 26, 27, 30, 31, 32, 33, 34, 36, 39, 40, 41, 44, 45, 47, 48, 50, 51, 52, 54, 55, 59, 60, 62, 64, 65, 66, 67, 68, 72, 75, 78, 80, 81, 82, 83, 85, 88, 90, 93, 94, 96, 99, 100, 102, 104, 108
Offset: 1

Views

Author

Gus Wiseman, Sep 12 2022

Keywords

Comments

An interval such as {3,4,5} is a set of positive integers with all differences of adjacent elements equal to 1.
A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
We define the multiset of multisets with MM-number n to be formed by taking the multiset of prime indices of each part of the multiset of prime indices of n. The size of this multiset of multisets is A302242(n). For example, the prime indices of 78 are {1,2,6}, so the multiset of multisets with MM-number 78 is {{},{1},{1,2}}.

Examples

			The initial terms and corresponding multisets of multisets:
   1: {}
   2: {{}}
   3: {{1}}
   4: {{},{}}
   5: {{2}}
   6: {{},{1}}
   8: {{},{},{}}
   9: {{1},{1}}
  10: {{},{2}}
  11: {{3}}
  12: {{},{},{1}}
  13: {{1,2}}
  15: {{1},{2}}
  16: {{},{},{},{}}
		

Crossrefs

The initial version is A356940.
Intervals are counted by A000012, A001227, ranked by A073485.
Other types: A107742, A356936, A356937, A356938.
Other conditions: A302478, A302492, A356930, A356935, A356944, A356955.
A000041 counts integer partitions, strict A000009.
A000688 counts factorizations into prime powers.
A001055 counts factorizations.
A001221 counts prime divisors, sum A001414.
A001222 counts prime factors with multiplicity.
A056239 adds up prime indices, row sums of A112798.

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    chQ[y_]:=Or[Length[y]<=1,Union[Differences[y]]=={1}];
    Select[Range[100],And@@chQ/@primeMS/@primeMS[#]&]

A356938 Number of multisets of intervals whose multiset union is of size n and covers an initial interval of positive integers with weakly decreasing multiplicities.

Original entry on oeis.org

1, 1, 3, 7, 18, 41, 101, 228, 538, 1209
Offset: 0

Views

Author

Gus Wiseman, Sep 09 2022

Keywords

Comments

An interval such as {3,4,5} is a set of positive integers with all differences of adjacent elements equal to 1.

Examples

			The a(1) = 1 through a(4) = 18 multiset partitions:
  {{1}}  {{1,2}}    {{1,2,3}}      {{1,2,3,4}}
         {{1},{1}}  {{1},{1,2}}    {{1},{1,2,3}}
         {{1},{2}}  {{1},{2,3}}    {{1,2},{1,2}}
                    {{3},{1,2}}    {{1},{2,3,4}}
                    {{1},{1},{1}}  {{1,2},{3,4}}
                    {{1},{1},{2}}  {{4},{1,2,3}}
                    {{1},{2},{3}}  {{1},{1},{1,2}}
                                   {{1},{1},{2,3}}
                                   {{1},{2},{1,2}}
                                   {{1},{2},{3,4}}
                                   {{1},{3},{1,2}}
                                   {{1},{4},{2,3}}
                                   {{3},{4},{1,2}}
                                   {{1},{1},{1},{1}}
                                   {{1},{1},{1},{2}}
                                   {{1},{1},{2},{2}}
                                   {{1},{1},{2},{3}}
                                   {{1},{2},{3},{4}}
		

Crossrefs

A000041 counts integer partitions, strict A000009.
A000670 counts patterns, ranked by A333217, necklace A019536.
A011782 counts multisets covering an initial interval.
Intervals are counted by A000012, A001227, ranked by A073485.
Other conditions: A035310, A063834, A330783, A356934.

Programs

  • Mathematica
    strnorm[n_]:=Flatten[MapIndexed[Table[#2,{#1}]&,#]]&/@IntegerPartitions[n];
    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]]]];
    chQ[y_]:=Or[Length[y]<=1,Union[Differences[y]]=={1}];
    Table[Length[Select[Join@@mps/@strnorm[n],And@@chQ/@#&]],{n,0,5}]

A356942 Number of multisets of gapless multisets whose multiset union is a size-n multiset covering an initial interval.

Original entry on oeis.org

1, 1, 4, 15, 61, 249, 1040, 4363, 18424, 78014, 331099, 1407080, 5985505, 25477399, 108493103, 462147381, 1969025286, 8390475609, 35757524184, 152398429323, 649555719160, 2768653475487, 11801369554033, 50304231997727, 214428538858889, 914039405714237
Offset: 0

Views

Author

Gus Wiseman, Sep 08 2022

Keywords

Comments

A multiset is gapless if it covers an interval of positive integers. For example, {2,3,3,4} is gapless but {1,1,3,3} is not.

Examples

			The a(1) = 1 through a(3) = 14 multiset partitions:
  {{1}}  {{1,1}}    {{1,1,1}}
         {{1,2}}    {{1,1,2}}
         {{1},{1}}  {{1,2,2}}
         {{1},{2}}  {{1,2,3}}
                    {{1},{1,1}}
                    {{1},{1,2}}
                    {{1},{2,2}}
                    {{1},{2,3}}
                    {{2},{1,1}}
                    {{2},{1,2}}
                    {{3},{1,2}}
                    {{1},{1},{1}}
                    {{1},{1},{2}}
                    {{1},{2},{2}}
                    {{1},{2},{3}}
		

Crossrefs

A000041 counts integer partitions, strict A000009.
A000670 counts patterns, ranked by A333217, necklace A019536.
A011782 counts multisets covering an initial interval.
Gapless multisets are counted by A034296, ranked by A073491.
Other conditions: A034691, A055887, A116540, A255906, A356933, A356937.
Other types of multiset partitions: A356233, A356941, A356943, A356944.

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]];
    nogapQ[m_]:=Or[m=={},Union[m]==Range[Min[m],Max[m]]];
    Table[Length[Select[Join@@mps/@allnorm[n],And@@nogapQ/@#&]],{n,0,5}]
  • PARI
    EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)}
    R(n,k) = {EulerT(vector(n, j, sum(i=1, min(k, j), (k-i+1)*binomial(j-1, i-1))))}
    seq(n) = {my(A=1+O(y*y^n)); for(k = 1, n, A += x^k*(1 + y*Ser(R(n,k), y) - polcoef(1/(1 - x*A) + O(x^(k+2)), k+1))); Vec(subst(A,x,1))} \\ Andrew Howroyd, Jan 01 2023

Extensions

Terms a(9) and beyond from Andrew Howroyd, Jan 01 2023

A356933 Number of multisets of multisets, each of odd size, whose multiset union is a size-n multiset covering an initial interval.

Original entry on oeis.org

1, 1, 2, 8, 28, 108, 524, 2608, 14176, 86576, 550672, 3782496, 27843880, 214071392, 1751823600, 15041687664, 134843207240, 1269731540864, 12427331494304, 126619822952928, 1341762163389920, 14712726577081248, 167209881188545344, 1963715680476759040, 23794190474350155856
Offset: 0

Views

Author

Gus Wiseman, Sep 08 2022

Keywords

Examples

			The a(4) = 28 multiset partitions:
  {1}{111}      {1}{112}      {1}{123}      {1}{234}
  {1}{1}{1}{1}  {1}{122}      {1}{223}      {2}{134}
                {1}{222}      {1}{233}      {3}{124}
                {2}{111}      {2}{113}      {4}{123}
                {2}{112}      {2}{123}      {1}{2}{3}{4}
                {2}{122}      {2}{133}
                {1}{1}{1}{2}  {3}{112}
                {1}{1}{2}{2}  {3}{122}
                {1}{2}{2}{2}  {3}{123}
                              {1}{1}{2}{3}
                              {1}{2}{2}{3}
                              {1}{2}{3}{3}
		

Crossrefs

A000041 counts integer partitions, strict A000009.
A000670 counts patterns, ranked by A333217, necklace A019536.
A011782 counts multisets covering an initial interval.
Odd-size multisets are counted by A000302, A027193, A058695, ranked by A026424.
Other conditions: A034691, A116540, A255906, A356937, A356942.
Other types: A050330, A356932, A356934, A356935.

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]];
    Table[Length[Select[Join@@mps/@allnorm[n],OddQ[Times@@Length/@#]&]],{n,0,5}]
  • PARI
    EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)}
    R(n,k) = {EulerT(vector(n, j, if(j%2 == 1, binomial(j+k-1, j))))}
    seq(n) = {concat([1], sum(k=1, n, R(n, k)*sum(r=k, n, binomial(r, k)*(-1)^(r-k)) ))} \\ Andrew Howroyd, Jan 01 2023

Extensions

Terms a(9) and beyond from Andrew Howroyd, Jan 01 2023

A356936 Number of multiset partitions of the multiset of prime indices of n into intervals. Number of factorizations of n into members of A073485.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 2, 3, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 1, 2, 1, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1
Offset: 1

Views

Author

Gus Wiseman, Sep 08 2022

Keywords

Comments

An interval is a set of positive integers with all differences of adjacent elements equal to 1.
A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.

Examples

			The a(n) multiset partitions for n = 6, 30, 36, 90, 180:
  {12}    {123}      {12}{12}      {12}{23}      {12}{123}
  {1}{2}  {1}{23}    {1}{2}{12}    {2}{123}      {1}{12}{23}
          {3}{12}    {1}{1}{2}{2}  {1}{2}{23}    {1}{2}{123}
          {1}{2}{3}                {2}{3}{12}    {3}{12}{12}
                                   {1}{2}{2}{3}  {1}{1}{2}{23}
                                                 {1}{2}{3}{12}
                                                 {1}{1}{2}{2}{3}
The a(n) factorizations for n = 6, 30, 36, 90, 180:
  (6)    (30)     (6*6)      (3*30)     (6*30)
  (2*3)  (5*6)    (2*3*6)    (6*15)     (5*6*6)
         (2*15)   (2*2*3*3)  (3*5*6)    (2*3*30)
         (2*3*5)             (2*3*15)   (2*6*15)
                             (2*3*3*5)  (2*3*5*6)
                                        (2*2*3*15)
                                        (2*2*3*3*5)
		

Crossrefs

A000688 counts factorizations into prime powers.
A001055 counts factorizations.
A001221 counts prime divisors, sum A001414.
A001222 counts prime factors with multiplicity.
A356069 counts gapless divisors, initial A356224 (complement A356225).
A056239 adds up prime indices, row sums of A112798.
Intervals are counted by A000012, A001227, ranked by A073485.
Other conditions: A050320, A050330, A322585, A356931, A356945.

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]];
    chQ[y_]:=Or[Length[y]<=1,Union[Differences[y]]=={1}];
    Table[Length[Select[facs[n],And@@chQ/@primeMS/@#&]],{n,100}]

A356957 Number of set partitions of strict integer partitions of n into intervals, where an interval is a set of positive integers with all differences of adjacent elements equal to 1.

Original entry on oeis.org

1, 1, 1, 3, 2, 4, 7, 7, 8, 13, 20, 19, 27, 30, 42, 60, 63, 75, 99, 112, 141, 191, 205, 248, 296, 357, 408, 513, 617, 696, 831, 969, 1117, 1337, 1523, 1797, 2171, 2420, 2805, 3265, 3772, 4289, 5013, 5661, 6579, 7679, 8615, 9807, 11335, 12799, 14581
Offset: 0

Views

Author

Gus Wiseman, Sep 13 2022

Keywords

Examples

			The a(1) = 1 through a(6) = 7 set partitions:
  {{1}}  {{2}}  {{3}}      {{4}}      {{5}}      {{6}}
                {{1,2}}    {{1},{3}}  {{2,3}}    {{1,2,3}}
                {{1},{2}}             {{1},{4}}  {{1},{5}}
                                      {{2},{3}}  {{2},{4}}
                                                 {{1},{2,3}}
                                                 {{1,2},{3}}
                                                 {{1},{2},{3}}
		

Crossrefs

Intervals are counted by A000012, A001227, ranked by A073485.
The initial version is A010054.
For set partitions of {1..n} we have A011782.
The non-strict version is A107742
Not restricting to intervals gives A294617.
A000041 counts integer partitions, strict A000009.
A000110 counts set partitions.
A001970 counts multiset partitions of integer partitions.
A356941 counts multiset partitions of integer partitions w/ gapless blocks.

Programs

  • Mathematica
    chQ[y_] := Length[y] <= 1 || Union[Differences[y]] == {1};
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    Table[Length[Select[Join@@sps/@Reverse/@Select[IntegerPartitions[n], UnsameQ@@#&],And@@chQ/@#&]],{n,0,15}]
Showing 1-6 of 6 results.