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A286187
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Number of connected induced (non-null) subgraphs of the web graph with 3n nodes.
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15
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6, 33, 188, 985, 4990, 24645, 119712, 574225, 2727218, 12847821, 60115060, 279652793, 1294441894, 5965567125, 27387631368, 125308264225, 571591760602, 2600204421405, 11799376912220, 53424388364873, 241398575303374, 1088727972172389, 4901842528232304, 22034981672761649
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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Andrew Howroyd, Table of n, a(n) for n = 1..200
Eric Weisstein's World of Mathematics, Vertex-Induced Subgraph
Eric Weisstein's World of Mathematics, Web Graph
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FORMULA
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Empirical g.f.: x*(6 - 39*x + 92*x^2 - 101*x^3 + 32*x^4 - 8*x^5 + 64*x^6 - 48*x^7) / ((1 - x)^2*(1 - 5*x + 2*x^2 + 4*x^3)^2). - Colin Barker, May 21 2017
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MATHEMATICA
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{6, 33} ~Join~ Table[g = GraphData[{"Web", n}]; -1 + ParallelSum[Boole@ ConnectedGraphQ@ Subgraph[g, s], {s, Subsets@ Range[3 n]}], {n, 3, 6}]
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CROSSREFS
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Cf. A020873 (wheel), A059020 (ladder), A059525 (grid), A286139 (king), A286182 (prism), A286183 (antiprism), A286184 (helm), A286185 (Möbius ladder), A286186 (friendship), A286188 (gear), A286189 (rook), A285765 (queen).
Sequence in context: A297221 A006630 A180035 * A260774 A218182 A093964
Adjacent sequences: A286184 A286185 A286186 * A286188 A286189 A286190
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KEYWORD
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nonn
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AUTHOR
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Giovanni Resta, May 04 2017
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EXTENSIONS
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a(12)-a(24) from Andrew Howroyd, May 20 2017
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STATUS
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approved
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