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 A005327 Certain subgraphs of a directed graph (inverse binomial transform of A005321). (Formerly M4289) 7
 1, 0, 1, 6, 91, 2820, 177661, 22562946, 5753551231, 2940064679040, 3007686166657921, 6156733583148764286, 25211824022994189751171, 206510050572345408251841660, 3383254158526734823389921915781 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS q-Subfactorial for q=2. - Vladimir Reshetnikov, Sep 12 2016 REFERENCES T. L. Greenough, Enumeration of interval orders without duplicated holdings, Preprint, circa 1976. T. L. Greenough, T. Lockman, Representation and enumeration of interval orders and semiorders, Ph.D. Thesis, Dartmouth,1976. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS G. C. Greubel, Table of n, a(n) for n = 1..50 E. Andresen, K. Kjeldsen, On certain subgraphs of a complete transitively directed graph, Discrete Math. 14 (1976), no. 2, 103-119. T. L. Greenough, Enumeration of interval orders without duplicated holdings, Preprint, circa 1976. [Annotated scanned copy] N. J. A. Sloane, Transforms Eric Weisstein's World of Mathematics, Subfactorial, q-Factorial, q-Analog. FORMULA For n>1, a(n) = (2^(n-1)-1)*a(n-1) + (-1)^(n-1). - Max Alekseyev, Feb 23 2012 a(n) = p(n-1)*sum((-1)^j/p(j), j=0..n-1), where p(0) = 1, p(k) = product(2^i-1, i=1..k) for k>0. - Emeric Deutsch, Jan 23 2005 a(n) ~ A048651^2 * 2^(n*(n-1)/2). - Vaclav Kotesovec, Oct 09 2019 MAPLE p:=proc(n) if n=0 then 1 else product(2^i-1, i=1..n) fi end: a:=n->p(n-1)*sum((-1)^j/p(j), j=0..n-1): seq(a(n), n=1..17); # Emeric Deutsch, Jan 23 2005 MATHEMATICA a[1] = 1; a[n_] := a[n] = (2^(n-1)-1)*a[n-1] + (-1)^(n-1); Array[a, 15] (* Jean-François Alcover, Apr 05 2016, after Max Alekseyev *) With[{q = 2}, Table[QFactorial[n, q] Sum[(-1)^k/QFactorial[k, q], {k, 0, n}], {n, 0, 20}]] (* Vladimir Reshetnikov, Sep 12 2016 *) CROSSREFS Cf. A002820, A005329, A005321. Sequence in context: A246155 A219220 A006151 * A182263 A171910 A278683 Adjacent sequences:  A005324 A005325 A005326 * A005328 A005329 A005330 KEYWORD nonn AUTHOR EXTENSIONS More terms from Max Alekseyev, Apr 27 2010 STATUS approved

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Last modified August 13 06:22 EDT 2020. Contains 336442 sequences. (Running on oeis4.)