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A003292
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Number of 4-line partitions of n decreasing across rows.
(Formerly M1050)
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0
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1, 2, 4, 7, 11, 19, 29, 46, 70, 106, 156, 232, 334, 482, 686, 971, 1357, 1894, 2612, 3592, 4900, 6656, 8980, 12077, 16137, 21490, 28476, 37600, 49422, 64763, 84511
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| a(n) is the number of unlabeled graphs on n nodes whose connected components are a path or a cycle. - Geoffrey Critzer, Nov 28 2011
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REFERENCES
| M. S. Cheema and W. E. Conway, Numerical investigation of certain asymptotic results in the theory of partitions, Math. Comp., 26 (1972), 999-1005.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Herbert Wilf, Generatingfunctiontology, Academic Press, 1994, page 106.
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FORMULA
| G.f.: Product (1 - x^k)^-{c(k)}; c(k) = 1, 1, 2, 2, 2, 2, ....
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MATHEMATICA
| p=Product[1/(1-x^i), {i, 1, 20}]; CoefficientList[Series[p^2(1-x)(1-x^2), {x, 0, 20}], x] (* Geoffrey Critzer, Nov 28 2011 *)
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CROSSREFS
| Sequence in context: A024622 A034337 A083024 * A007864 A192670 A118647
Adjacent sequences: A003289 A003290 A003291 * A003293 A003294 A003295
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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