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A030236
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Cycle-path coverings of a family of digraphs.
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1
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1, 2, 7, 18, 49, 136, 377, 1044, 2891, 8006, 22171, 61398, 170029, 470860, 1303949, 3611016, 9999959, 27692810, 76689487, 212375610, 588130153, 1628704336, 4510358465, 12490501212, 34589849507, 95789405774, 265268869027
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| O. M. D'Antona and E. Munarini, The Cycle-path Indicator Polynomial of a Digraph, Advances in Applied Mathematics 25 (2000), 41-56.
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FORMULA
| a(n+4) = 3 a(n+3) - a(n+2) + a(n+1), n >= 0; a(n+3) = 2*a(n+2) + a(n+1) + 2*sum( a(i), i = 0..n ), n >= 0; G.f.: (1-t+2*t^2-2*t^3)/(1-3*t+t^2-t^3)
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CROSSREFS
| Cf. A030186.
Sequence in context: A022726 A192873 A017925 * A074141 A122931 A094976
Adjacent sequences: A030233 A030234 A030235 * A030237 A030238 A030239
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KEYWORD
| nonn,easy
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AUTHOR
| Ottavio D'Antona (dantona(AT)dsi.unimi.it) and Emanuele Munarini (munarini(AT)mate.polimi.it).
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