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 A005330 Certain subgraphs of a directed graph. (Formerly M3992) 2
 1, 5, 40, 644, 21496, 1471460, 204062440, 56865072164, 31688930152696, 35223651007587140, 78001790003385408040, 343983307379873262633284, 3020895063527811952260491896, 52843677532033943174017588842020, 1841795434229559227318546660111716840 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Table of n, a(n) for n=2..16. E. Andresen, K. Kjeldsen, On certain subgraphs of a complete transitively directed graph, Discrete Math. 14 (1976), no. 2, 103-119. FORMULA a(n) = Sum_{i=0..n-2} (C(n-1, i) * p(n-1-i) * Sum_{j=0..n-2-i} (-1)^j * (n-1-i-j) / p(j) where p(n) = Product_{k=1..n} (2^k-1). - Sean A. Irvine, May 10 2016 PROG (PARI) p(n) = prod(k=1, n, 2^k-1); a(n) = sum(i=0, n-2, binomial(n-1, i) * p(n-1-i) * sum(j=0, n-2-i, (-1)^j * (n-1-i-j) / p(j))); \\ Michel Marcus, May 10 2016 CROSSREFS Sequence in context: A280572 A217904 A357796 * A003084 A010573 A326265 Adjacent sequences: A005327 A005328 A005329 * A005331 A005332 A005333 KEYWORD nonn AUTHOR N. J. A. Sloane EXTENSIONS More terms from Sean A. Irvine, May 10 2016 STATUS approved

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Last modified August 9 13:53 EDT 2024. Contains 375042 sequences. (Running on oeis4.)