A321407 Number of non-isomorphic multiset partitions of weight n with no constant parts.

1, 0, 1, 2, 7, 13, 47, 111, 367, 1057, 3474, 11116, 38106, 131235, 470882, 1720959, 6472129, 24860957, 97779665, 392642763, 1610045000, 6732768139, 28699327441, 124600601174, 550684155992, 2476019025827, 11320106871951, 52598300581495, 248265707440448, 1189855827112636, 5787965846277749

Offset

0,4

Comments

Also the number of nonnegative integer matrices up to row and column permutations with sum of elements equal to n and no zero rows or columns, in which every row has at least two nonzero entries.

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

Links

Andrew Howroyd, Table of n, a(n) for n = 0..50

Example

Non-isomorphic representatives of the a(2) = 1 through a(5) = 13 multiset partitions:
  {{1,2}}  {{1,2,2}}  {{1,1,2,2}}    {{1,1,2,2,2}}
           {{1,2,3}}  {{1,2,2,2}}    {{1,2,2,2,2}}
                      {{1,2,3,3}}    {{1,2,2,3,3}}
                      {{1,2,3,4}}    {{1,2,3,3,3}}
                      {{1,2},{1,2}}  {{1,2,3,4,4}}
                      {{1,2},{3,4}}  {{1,2,3,4,5}}
                      {{1,3},{2,3}}  {{1,2},{1,2,2}}
                                     {{1,2},{2,3,3}}
                                     {{1,2},{3,4,4}}
                                     {{1,2},{3,4,5}}
                                     {{1,3},{2,3,3}}
                                     {{1,4},{2,3,4}}
                                     {{2,3},{1,2,3}}

Prog

(PARI)
EulerT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, 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)={EulerT(Vec(sum(j=1, #q, my(g=gcd(t, q[j])); g*x^(q[j]/g)) + O(x*x^k), -k))}
S(q, t, k)={sum(j=1, #q, if(t%q[j]==0, q[j]))*vector(k, i, 1)}
a(n)={if(n==0, 1, my(s=0); forpart(q=n, s+=permcount(q)*polcoef(exp(sum(t=1, n, subst(x*Ser(K(q, t, n\t)-S(q, t, n\t))/t, x, x^t) )), n)); s/n!)} \\ Andrew Howroyd, Jan 17 2023

Crossrefs

Cf. A001970, A007716, A050535, A055884, A120733, A317533, A320798, A320801, A320808, A321760.

Sequence in context: A129592 A153136 A178607 * A127487 A226140 A180003

Adjacent sequences: A321404 A321405 A321406 * A321408 A321409 A321410

Keyword

nonn

Author

Gus Wiseman, Nov 29 2018

Extensions

Terms a(11) and beyond from Andrew Howroyd, Jan 17 2023

Status

approved