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 A005387 Number of partitional matroids on n elements. (Formerly M1493) 2
 1, 2, 5, 16, 62, 276, 1377, 7596, 45789, 298626, 2090910, 15621640, 123897413, 1038535174, 9165475893, 84886111212, 822648571314, 8321077557124, 87648445601429, 959450073912136, 10894692556576613, 128114221270929646 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES 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). LINKS 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 FORMULA E.g.f.: exp ((x-1)*e^x + 2*x + 1 ). MATHEMATICA 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 *) CROSSREFS Sequence in context: A033543 A124531 A129578 * A173469 A138549 A210667 Adjacent sequences:  A005384 A005385 A005386 * A005388 A005389 A005390 KEYWORD nonn,easy,nice AUTHOR EXTENSIONS More terms from James A. Sellers, Aug 21 2000 STATUS approved

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Last modified April 11 00:03 EDT 2021. Contains 342877 sequences. (Running on oeis4.)