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A005387
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Number of partitional matroids on n elements.
(Formerly M1493)
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2
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1, 2, 5, 16, 62, 276, 1377, 7596, 45789, 298626, 2090910, 15621640, 123897413, 1038535174, 9165475893, 84886111212, 822648571314, 8321077557124, 87648445601429, 959450073912136, 10894692556576613, 128114221270929646
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OFFSET
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0,2
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REFERENCES
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Recski, A.; Enumerating partitional matroids. Stud. Sci. Math. Hungar. 9 (1974), 247-249 (1975).
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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T. D. Noe, Table of n, a(n) for n=0..100
A. Recski, Enumerating partitional matroids, Preprint.
A. Recski & N. J. A. Sloane, Correspondence, 1975
Index entries for sequences related to matroids
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FORMULA
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E.g.f.: exp ((x-1)*e^x + 2*x + 1 ).
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MATHEMATICA
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With[{nn=30}, CoefficientList[Series[Exp[(x-1)E^x+2x+1], {x, 0, nn}], x]Range[0, nn]!] (* Harvey P. Dale, Nov 22 2012 *)
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CROSSREFS
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Sequence in context: A033543 A124531 A129578 * A173469 A138549 A210667
Adjacent sequences: A005384 A005385 A005386 * A005388 A005389 A005390
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KEYWORD
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nonn,easy,nice
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AUTHOR
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N. J. A. Sloane.
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EXTENSIONS
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More terms from James A. Sellers, Aug 21 2000
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STATUS
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approved
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