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Number of normal multiset partitions of weight n where every part has the same average.
9

%I #6 Jul 13 2019 09:12:29

%S 1,1,3,7,17,35,103,197

%N Number of normal multiset partitions of weight n where every part has the same average.

%C A multiset partition is normal if it covers an initial interval of positive integers.

%H Gus Wiseman, <a href="/A038041/a038041.txt">Sequences counting and ranking multiset partitions whose part lengths, sums, or averages are constant or strict.</a>

%e The a(0) = 1 through a(4) = 17 normal multiset partitions where every part has the same average:

%e {} {{1}} {{1,1}} {{1,1,1}} {{1,1,1,1}}

%e {{1,2}} {{1,1,2}} {{1,1,1,2}}

%e {{1},{1}} {{1,2,2}} {{1,1,2,2}}

%e {{1,2,3}} {{1,1,2,3}}

%e {{1},{1,1}} {{1,2,2,2}}

%e {{2},{1,3}} {{1,2,2,3}}

%e {{1},{1},{1}} {{1,2,3,3}}

%e {{1,2,3,4}}

%e {{1},{1,1,1}}

%e {{1,1},{1,1}}

%e {{1,2},{1,2}}

%e {{1,3},{2,2}}

%e {{1,4},{2,3}}

%e {{2},{1,2,3}}

%e {{1},{1},{1,1}}

%e {{2},{2},{1,3}}

%e {{1},{1},{1},{1}}

%t sps[{}]:={{}};sps[set:{i_,___}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,___}];

%t mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];

%t allnorm[n_]:=If[n<=0,{{}},Function[s,Array[Count[s,y_/;y<=#]+1&,n]]/@Subsets[Range[n-1]+1]];

%t Table[Length[Select[Join@@mps/@allnorm[n],SameQ@@Mean/@#&]],{n,0,5}]

%Y Cf. A038041, A051293, A255906, A317583, A326512, A326515, A326517, A326518, A326519, A326521, A326536.

%K nonn,more

%O 0,3

%A _Gus Wiseman_, Jul 12 2019