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A290756
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Number of (non-null) connected induced subgraphs of the complete tripartite graph K_{n,n,n}.
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1
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7, 60, 499, 4062, 32689, 261972, 2096791, 16776474, 134216221, 1073738784, 8589928483, 68719464486, 549755789353, 4398046461996, 35184371990575, 281474976514098, 2251799813292085, 18014398508695608, 144115188074283067, 1152921504603701310
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OFFSET
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1,1
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COMMENTS
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The only disconnected induced subgraphs are those constructed from the vertices of a single partition. - Andrew Howroyd, Aug 10 2017
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LINKS
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FORMULA
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a(n) = 12*a(n-1) - 37*a(n-2) + 42*a(n-3) - 16*a(n-4).
G.f.: (x (7 - 24 x + 38 x^2))/((-1 + x)^2 (1 - 10 x + 16 x^2)).
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MATHEMATICA
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Table[8^n - 3 2^n + 3 n + 2, {n, 20}]
LinearRecurrence[{12, -37, 42, -16}, {7, 60, 499, 4062}, 20]
CoefficientList[Series[(7 - 24 x + 38 x^2)/((-1 + x)^2 (1 - 10 x + 16 x^2)), {x, 0, 20}], x]
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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