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 A320768 Number of set partitions of the set of nonempty subsets of {1,...,n} using set partitions. 2
 1, 1, 2, 15, 2420 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Table of n, a(n) for n=0..4. EXAMPLE The a(3) = 15 set partitions: {{{1}},{{2}},{{3}},{{1,2}},{{1,3}},{{2,3}},{{1,2,3}}} {{{1}},{{2}},{{3},{1,2}},{{1,3}},{{2,3}},{{1,2,3}}} {{{1}},{{2},{3}},{{1,2}},{{1,3}},{{2,3}},{{1,2,3}}} {{{1}},{{2},{1,3}},{{3}},{{1,2}},{{2,3}},{{1,2,3}}} {{{1}},{{2},{1,3}},{{3},{1,2}},{{2,3}},{{1,2,3}}} {{{1},{2}},{{3}},{{1,2}},{{1,3}},{{2,3}},{{1,2,3}}} {{{1},{2}},{{3},{1,2}},{{1,3}},{{2,3}},{{1,2,3}}} {{{1},{3}},{{2}},{{1,2}},{{1,3}},{{2,3}},{{1,2,3}}} {{{1},{3}},{{2},{1,3}},{{1,2}},{{2,3}},{{1,2,3}}} {{{1},{2,3}},{{2}},{{3}},{{1,2}},{{1,3}},{{1,2,3}}} {{{1},{2,3}},{{2}},{{3},{1,2}},{{1,3}},{{1,2,3}}} {{{1},{2,3}},{{2},{3}},{{1,2}},{{1,3}},{{1,2,3}}} {{{1},{2,3}},{{2},{1,3}},{{3}},{{1,2}},{{1,2,3}}} {{{1},{2,3}},{{2},{1,3}},{{3},{1,2}},{{1,2,3}}} {{{1},{2},{3}},{{1,2}},{{1,3}},{{2,3}},{{1,2,3}}} MATHEMATICA spsu[_, {}]:={{}}; spsu[foo_, set:{i_, ___}]:=Join@@Function[s, Prepend[#, s]&/@spsu[Select[foo, Complement[#, Complement[set, s]]=={}&], Complement[set, s]]]/@Cases[foo, {i, ___}]; sps[set_]:=spsu[Rest[Subsets[set]], set]; Table[Length[spsu[Sort/@Union@@sps/@Rest[Subsets[Range[n]]], Rest[Subsets[Range[n]]]]], {n, 4}] CROSSREFS Cf. A000110, A000258, A008277, A318391, A318392, A318393, A318394, A319884. Sequence in context: A359849 A096232 A193869 * A337799 A064171 A365628 Adjacent sequences: A320765 A320766 A320767 * A320769 A320770 A320771 KEYWORD nonn,more AUTHOR Gus Wiseman, Dec 09 2018 STATUS approved

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Last modified July 18 17:21 EDT 2024. Contains 374388 sequences. (Running on oeis4.)