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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A321403 Number of non-isomorphic self-dual set multipartitions (multisets of sets) of weight n.

Original entry on oeis.org

1, 1, 1, 2, 4, 6, 10, 17, 32, 56, 98, 177, 335, 620, 1164, 2231, 4349, 8511, 16870, 33844, 68746, 140894, 291698, 610051, 1288594, 2745916, 5903988, 12805313, 28010036, 61764992, 137281977, 307488896, 693912297, 1577386813, 3611241900, 8324940862, 19321470086
Offset: 0

Views

Author

Gus Wiseman, Nov 15 2018

Keywords

Comments

Also the number of symmetric (0,1)-matrices up to row and column permutations with sum of elements equal to n and no zero rows or columns.
The dual of a multiset partition has, for each vertex, one part consisting of the indices (or positions) of the parts containing that vertex, counted with multiplicity. For example, the dual of {{1,2},{2,2}} is {{1},{1,2,2}}.
The weight of a multiset partition is the sum of sizes of its parts. Weight is generally not the same as number of vertices.

Examples

			Non-isomorphic representatives of the a(1) = 1 through a(7) = 17 set multipartitions:
  {{1}}  {{1},{2}}  {{2},{1,2}}    {{1,2},{1,2}}      {{1},{2,3},{2,3}}
                    {{1},{2},{3}}  {{1},{1},{2,3}}    {{2},{1,3},{2,3}}
                                   {{1},{3},{2,3}}    {{3},{3},{1,2,3}}
                                   {{1},{2},{3},{4}}  {{1},{2},{2},{3,4}}
                                                      {{1},{2},{4},{3,4}}
                                                      {{1},{2},{3},{4},{5}}
.
  {{1,2},{1,3},{2,3}}        {{1,3},{2,3},{1,2,3}}
  {{3},{2,3},{1,2,3}}        {{1},{1},{1,4},{2,3,4}}
  {{1},{1},{1},{2,3,4}}      {{1},{2,3},{2,4},{3,4}}
  {{1},{2},{3,4},{3,4}}      {{1},{4},{3,4},{2,3,4}}
  {{1},{3},{2,4},{3,4}}      {{2},{1,2},{3,4},{3,4}}
  {{1},{4},{4},{2,3,4}}      {{2},{1,3},{2,4},{3,4}}
  {{2},{4},{1,2},{3,4}}      {{3},{4},{1,4},{2,3,4}}
  {{1},{2},{3},{3},{4,5}}    {{4},{4},{4},{1,2,3,4}}
  {{1},{2},{3},{5},{4,5}}    {{1},{1},{5},{2,3},{4,5}}
  {{1},{2},{3},{4},{5},{6}}  {{1},{2},{2},{2},{3,4,5}}
                             {{1},{2},{3},{4,5},{4,5}}
                             {{1},{2},{4},{3,5},{4,5}}
                             {{1},{2},{5},{5},{3,4,5}}
                             {{1},{3},{5},{2,3},{4,5}}
                             {{1},{2},{3},{4},{4},{5,6}}
                             {{1},{2},{3},{4},{6},{5,6}}
                             {{1},{2},{3},{4},{5},{6},{7}}
Inequivalent representatives of the a(6) = 10 matrices:
  [0 0 1] [1 1 0]
  [0 1 1] [1 0 1]
  [1 1 1] [0 1 1]
.
  [1 0 0 0] [1 0 0 0] [1 0 0 0] [1 0 0 0] [0 1 0 0]
  [1 0 0 0] [0 1 0 0] [0 0 1 0] [0 0 0 1] [0 0 0 1]
  [1 0 0 0] [0 0 1 1] [0 1 0 1] [0 0 0 1] [1 1 0 0]
  [0 1 1 1] [0 0 1 1] [0 0 1 1] [0 1 1 1] [0 0 1 1]
.
  [1 0 0 0 0] [1 0 0 0 0]
  [0 1 0 0 0] [0 1 0 0 0]
  [0 0 1 0 0] [0 0 1 0 0]
  [0 0 1 0 0] [0 0 0 0 1]
  [0 0 0 1 1] [0 0 0 1 1]
.
  [1 0 0 0 0 0]
  [0 1 0 0 0 0]
  [0 0 1 0 0 0]
  [0 0 0 1 0 0]
  [0 0 0 0 1 0]
  [0 0 0 0 0 1]

Links

Crossrefs

Cf. A007716, A049311, A135588, A135589, A138178, A283877, A316983, A319616.
Cf. A320796, A320797, A321403, A321404, A321405.

Programs

  • PARI
    permcount(v) = {my(m=1, s=0, k=0, t); for(i=1, #v, t=v[i]; k=if(i>1&&t==v[i-1], k+1, 1); m*=t*k; s+=t); s!/m}
c(p, k)={polcoef((prod(i=2, #p, prod(j=1, i-1, (1 + x^(2*lcm(p[i], p[j])) + O(x*x^k))^gcd(p[i], p[j]))) * prod(i=1, #p, my(t=p[i]); (1 + x^t + O(x*x^k))^(t%2)*(1 + x^(2*t) + O(x*x^k))^(t\2) )), k)}
a(n)={my(s=0); forpart(p=n, s+=permcount(p)*c(p, n)); s/n!} \\ Andrew Howroyd, May 31 2023

Extensions

Terms a(11) and beyond from Andrew Howroyd, May 31 2023

A321402 Number of non-isomorphic strict self-dual multiset partitions of weight n with no singletons.

Original entry on oeis.org

1, 0, 1, 1, 2, 4, 8, 14, 27, 53, 105
Offset: 0

Views

Author

Gus Wiseman, Nov 09 2018

Keywords

Comments

Also the number of nonnegative integer symmetric matrices up to row and column permutations with sum of elements equal to n and no zero rows or columns, in which the rows are all different and none sums to 1.
The dual of a multiset partition has, for each vertex, one part consisting of the indices (or positions) of the parts containing that vertex, counted with multiplicity. For example, the dual of {{1,2},{2,2}} is {{1},{1,2,2}}.
The weight of a multiset partition is the sum of sizes of its parts. Weight is generally not the same as number of vertices.

Examples

			Non-isomorphic representatives of the a(2) = 1 through a(7) = 14 multiset partitions:
  {{11}}  {{111}}  {{1111}}    {{11111}}    {{111111}}      {{1111111}}
                   {{11}{22}}  {{11}{122}}  {{111}{222}}    {{111}{1222}}
                               {{11}{222}}  {{112}{122}}    {{111}{2222}}
                               {{12}{122}}  {{11}{2222}}    {{112}{1222}}
                                            {{12}{1222}}    {{11}{22222}}
                                            {{22}{1122}}    {{12}{12222}}
                                            {{11}{22}{33}}  {{122}{1122}}
                                            {{12}{13}{23}}  {{22}{11222}}
                                                            {{11}{12}{233}}
                                                            {{11}{22}{233}}
                                                            {{11}{22}{333}}
                                                            {{11}{23}{233}}
                                                            {{12}{13}{233}}
                                                            {{13}{23}{123}}

Crossrefs

Cf. A000219, A007716, A059201, A302545, A316980, A316983, A319560, A319616.
Cf. A320796, A320797, A320798, A320804, A320811, A320812, A321401, A321404, A321405, A321406, A321407.

A321677 Number of non-isomorphic set multipartitions (multisets of sets) of weight n with no singletons.

Original entry on oeis.org

1, 0, 1, 1, 4, 4, 16, 22, 70, 132, 375, 848, 2428, 6256, 18333, 52560, 161436, 500887, 1624969, 5384625, 18438815, 64674095, 233062429, 859831186, 3248411250, 12545820860, 49508089411, 199410275018, 819269777688, 3430680180687, 14633035575435, 63535672197070
Offset: 0

Views

Author

Gus Wiseman, Nov 16 2018

Keywords

Comments

The weight of a multiset partition is the sum of sizes of its parts. Weight is generally not the same as number of vertices.

Examples

			Non-isomorphic representatives of the a(2) = 1 through a(6) = 16 set multipartitions:
  {{1,2}}  {{1,2,3}}  {{1,2,3,4}}    {{1,2,3,4,5}}    {{1,2,3,4,5,6}}
                      {{1,2},{1,2}}  {{1,2},{3,4,5}}  {{1,2,3},{1,2,3}}
                      {{1,2},{3,4}}  {{1,4},{2,3,4}}  {{1,2},{3,4,5,6}}
                      {{1,3},{2,3}}  {{2,3},{1,2,3}}  {{1,2,3},{4,5,6}}
                                                      {{1,2,5},{3,4,5}}
                                                      {{1,3,4},{2,3,4}}
                                                      {{1,5},{2,3,4,5}}
                                                      {{3,4},{1,2,3,4}}
                                                      {{1,2},{1,2},{1,2}}
                                                      {{1,2},{1,3},{2,3}}
                                                      {{1,2},{3,4},{3,4}}
                                                      {{1,2},{3,4},{5,6}}
                                                      {{1,2},{3,5},{4,5}}
                                                      {{1,3},{2,3},{2,3}}
                                                      {{1,3},{2,4},{3,4}}
                                                      {{1,4},{2,4},{3,4}}

Links

Crossrefs

Cf. A000219, A007716, A049311, A283877, A302545, A316983, A319616.
Cf. A320797, A320798, A320804, A320811, A320812, A321404, A321406.

Programs

  • PARI
    WeighT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, n, (-1)^(n-1)/n))))-1, -#v)}
permcount(v) = {my(m=1, s=0, k=0, t); for(i=1, #v, t=v[i]; k=if(i>1&&t==v[i-1], k+1, 1); m*=t*k; s+=t); s!/m}
K(q, t, k)={WeighT(Vec(sum(j=1, #q, my(g=gcd(t, q[j])); g*x^(q[j]/g)) + O(x*x^k), -k)) - Vec(sum(j=1, #q, if(t%q[j]==0, q[j])) + O(x*x^k), -k)}
a(n)={if(n==0, 1, my(s=0); forpart(q=n, my(g=sum(t=1, n, subst(x*Ser(K(q, t, n\t)/t),x,x^t) )); s+=permcount(q)*polcoef(exp(g), n)); s/n!)} \\ Andrew Howroyd, Jan 16 2024

Extensions

Terms a(11) and beyond from Andrew Howroyd, Sep 01 2019
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