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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: A277405 A280572 A217904 * 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 November 18 17:21 EST 2019. Contains 329287 sequences. (Running on oeis4.)