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.
%I A320331 #5 Oct 11 2018 10:10:24 %S A320331 1,1,2,4,8,17,30,61,110,207,381,711,1250 %N A320331 Number of strict T_0 multiset partitions of integer partitions of n. %C A320331 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 T_0 condition means the dual is strict. %e A320331 The a(1) = 1 through a(5) = 17 multiset partitions: %e A320331 {{1}} {{2}} {{3}} {{4}} {{5}} %e A320331 {{1,1}} {{1,1,1}} {{2,2}} {{1,1,3}} %e A320331 {{1},{2}} {{1,1,2}} {{1,2,2}} %e A320331 {{1},{1,1}} {{1},{3}} {{1},{4}} %e A320331 {{1,1,1,1}} {{2},{3}} %e A320331 {{1},{1,2}} {{1,1,1,2}} %e A320331 {{2},{1,1}} {{1},{1,3}} %e A320331 {{1},{1,1,1}} {{1},{2,2}} %e A320331 {{2},{1,2}} %e A320331 {{3},{1,1}} %e A320331 {{1,1,1,1,1}} %e A320331 {{1},{1,1,2}} %e A320331 {{1,1},{1,2}} %e A320331 {{2},{1,1,1}} %e A320331 {{1},{1,1,1,1}} %e A320331 {{1,1},{1,1,1}} %e A320331 {{1},{2},{1,1}} %t A320331 sps[{}]:={{}};sps[set:{i_,___}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,___}]; %t A320331 mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]]; %t A320331 dual[eds_]:=Table[First/@Position[eds,x],{x,Union@@eds}]; %t A320331 Table[Length[Select[Join@@mps/@IntegerPartitions[n],And[UnsameQ@@#,UnsameQ@@dual[#]]&]],{n,8}] %Y A320331 Cf. A001970, A047968, A050342, A089259, A141268, A261049, A289501, A305551, A319066, A319312, A320328, A320330. %K A320331 nonn,more %O A320331 0,3 %A A320331 _Gus Wiseman_, Oct 11 2018