OFFSET
0,3
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..500
EXAMPLE
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}
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}]
PROG
(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
CROSSREFS
A011782 counts multisets covering an initial interval.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 08 2022
EXTENSIONS
Terms a(9) and beyond from Andrew Howroyd, Jan 01 2023
STATUS
approved