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A303027
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Number of free pure symmetric multifunctions with one atom, n positions, and no empty or unitary parts (subexpressions of the form x[] or x[y]).
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6
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1, 0, 0, 1, 1, 1, 3, 5, 7, 15, 28, 47, 90, 175, 319, 607, 1181, 2251, 4325, 8449, 16425, 31992, 62823, 123521, 243047, 480316, 951290, 1886293, 3749341, 7467815, 14893500, 29752398, 59532947, 119274491, 239275400, 480638121, 966571853, 1945901716, 3921699524
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OFFSET
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1,7
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COMMENTS
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Also the number of orderless Mathematica expressions with one atom, n positions, and no empty or unitary parts.
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LINKS
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EXAMPLE
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The a(10) = 15 Mathematica expressions:
o[o,o[o,o[o,o]]]
o[o,o[o,o][o,o]]
o[o[o,o],o[o,o]]
o[o,o][o,o[o,o]]
o[o,o[o,o]][o,o]
o[o,o][o,o][o,o]
o[o,o[o,o,o,o,o]]
o[o,o,o[o,o,o,o]]
o[o,o,o,o[o,o,o]]
o[o,o,o,o,o[o,o]]
o[o,o][o,o,o,o,o]
o[o,o,o][o,o,o,o]
o[o,o,o,o][o,o,o]
o[o,o,o,o,o][o,o]
o[o,o,o,o,o,o,o,o]
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MATHEMATICA
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allOLZR[n_]:=allOLZR[n]=If[n==1, {"o"}, Join@@Cases[Table[PR[k, n-k-1], {k, n-1}], PR[h_, g_]:>Join@@Table[Apply@@@Tuples[{allOLZR[h], Select[Union[Sort/@Tuples[allOLZR/@p]], Length[#]>1&]}], {p, IntegerPartitions[g]}]]];
Table[Length[allOLZR[n]], {n, 25}]
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PROG
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(PARI) EulerT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, n, 1/n))))-1, -#v)}
seq(n)={my(v=[1]); for(n=2, n, my(t=EulerT(v)-v); v=concat(v, sum(k=1, n-2, v[k]*t[n-k-1]))); v} \\ Andrew Howroyd, Aug 19 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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