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A005227
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Number of atomic species of degree n which are not nontrivial substitutions.
(Formerly M1029)
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2
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0, 1, 1, 2, 4, 6, 19, 20, 111, 116, 567, 641, 4718, 4772, 35489, 46012, 389277, 487408, 4616580
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OFFSET
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0,4
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REFERENCES
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Labelle, Jacques. Quelques espèces sur les ensembles de petite cardinalité, Ann. Sc. Math. Québec 9.1 (1985): 31-58.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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Define b(n), c(n), d(n): b(1)=d(1)=0. b(k)=a(k), k>1. c(k)=A000638(k), k>0, d(k)=A005226(k), k>1. d is Dirichlet convolution of b and c. - Christian G. Bower, Feb 23 2006
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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