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A000662
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Relations with 3 arguments on n nodes.
(Formerly M2180 N0872)
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2
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OFFSET
| 1,1
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REFERENCES
| F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, p. 76 (2.2.31)
W. Oberschelp, Kombinatorische Anzahlbestimmungen in Relationen, Math. Ann., 174 (1967), 53-78.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.
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FORMULA
| a(n) = sum {1*s_1+2*s_2+...=n} (fix A[s_1, s_2, ...]/(1^s_1*s_1!*2^s_2*s_2!*...)) where fix A[s_1, s_2, ...] = 2^sum {i, j, k>=1} (i*j*k*s_i*s_j*s_k/lcm(i, j, k)).
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CROSSREFS
| Cf. A000595, A001377, A051241.
Sequence in context: A014315 A097641 A065963 * A139907 A195379 A087619
Adjacent sequences: A000659 A000660 A000661 * A000663 A000664 A000665
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KEYWORD
| nonn,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Formula from Christian G. Bower (bowerc(AT)usa.net), Jan 06 2004
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