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 A006848 Number of extreme points of the set of n X n symmetric doubly-substochastic matrices. (Formerly M1515) 1
 1, 2, 5, 18, 75, 414, 2643, 20550, 180057, 1803330, 19925541, 242749602, 3218286195, 46082917278, 710817377715, 11689297807734, 205359276208113, 3812653265319810, 75092750890627077, 1553136587207991090, 33876594618751675611, 772263699644709647262 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Gheorghe Coserea, Table of n, a(n) for n = 0..200 Simon Plouffe, Master's Thesis, Uqam 1992, Approximations of generating functions and a few conjectures, arXiv:0911.4975 [math.NT], 2009. R. P. Stanley, Differentiably finite power series, European J. Combin., 1 (1980), 175-188. FORMULA The lgdegf is (2+x+x^4+x^5-2*x^3-2*x^2)/(x-1)^2/(x+1)^2, conjectured in Simon Plouffe's Master's Thesis, Uqam 1992. Lgdegf is the logarithmic derivative of f(x), the g.f. is exponential. MATHEMATICA Range[0, 21]! CoefficientList[Series[((1 + x)/(1 - x))^(1/4) Exp[(x (x^3 + 2 x^2 - x - 3))/(2 (x - 1) (x + 1))], {x, 0, 21}], x] (* Vincenzo Librandi, Aug 02 2015 *) PROG (PARI) Vec(serlaplace(((1+x)/(1-x))^(1/4) * exp((x*(x^3 + 2*x^2 - x - 3))/(2*(x-1)*(x+1)))) + O(x^33)) \\ Gheorghe Coserea, Aug 03 2015 CROSSREFS Sequence in context: A319121 A289655 A189281 * A208968 A206293 A137861 Adjacent sequences:  A006845 A006846 A006847 * A006849 A006850 A006851 KEYWORD nonn AUTHOR STATUS approved

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Last modified January 22 05:11 EST 2019. Contains 319353 sequences. (Running on oeis4.)