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A306416 Number of ordered set partitions of {1, ..., n} with no singletons or cyclical adjacencies (successive elements in the same block, where 1 is a successor of n). 2

%I #10 Feb 14 2019 19:26:24

%S 1,0,0,0,2,0,26,84,950,6000,62522,556116,6259598,69319848,874356338,

%T 11384093196,161462123894,2397736692144,37994808171962,

%U 631767062124564,11088109048500158,203828700127054008,3928762035148317314,79079452776283889820,1661265965479375937030,36332908076071038467520,826376466514358722894154

%N Number of ordered set partitions of {1, ..., n} with no singletons or cyclical adjacencies (successive elements in the same block, where 1 is a successor of n).

%H David Callan, <a href="https://arxiv.org/abs/math/0508052">On conjugates for set partitions and integer compositions</a>, arXiv:math/0508052 [math.CO], 2005.

%e The a(4) = 2 ordered set partitions are: {{1,3},{2,4}}, {{2,4},{1,3}}.

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

%t Table[Sum[Length[stn]!,{stn,Select[sps[Range[n]],And[Count[#,{_}]==0,Total[If[First[#]==1&&Last[#]==n,1,0]+Count[Subtract@@@Partition[#,2,1],-1]&/@#]==0]&]}],{n,0,10}]

%Y Cf. A000110, A000126, A000296, A000670, A001610, A032032 (adjacencies allowed), A052841 (singletons allowed), A124323, A169985, A306417, A324011 (orderless case), A324012, A324015.

%K nonn

%O 0,5

%A _Gus Wiseman_, Feb 14 2019

%E a(12)-a(26) from _Alois P. Heinz_, Feb 14 2019

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Last modified April 24 07:06 EDT 2024. Contains 371920 sequences. (Running on oeis4.)