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A052756
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A simple grammar.
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2
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0, 1, 6, 81, 1728, 50625, 1889568, 85766121, 4586471424, 282429536481, 19683000000000, 1531578985264449, 131621703842267136, 12381557655576425121, 1265437718438866624512, 139628860198736572265625
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,3
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LINKS
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Table of n, a(n) for n=0..15.
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 712
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FORMULA
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E.g.f.: -1/3*LambertW(-3*x)
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MAPLE
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spec := [S, {S=Prod(B, B, B, Z), B=Set(S)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A196909 A197076 A064341 * A193265 A138457 A204264
Adjacent sequences: A052753 A052754 A052755 * A052757 A052758 A052759
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KEYWORD
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easy,nonn
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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STATUS
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approved
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