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A335439
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a(n) = n*(n-1)/2 + 2^(n-1) - 1.
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1
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0, 2, 6, 13, 25, 46, 84, 155, 291, 556, 1078, 2113, 4173, 8282, 16488, 32887, 65671, 131224, 262314, 524477, 1048785, 2097382, 4194556, 8388883, 16777515, 33554756, 67109214, 134218105, 268435861, 536871346, 1073742288, 2147484143, 4294967823, 8589935152, 17179869778
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OFFSET
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1,2
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COMMENTS
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Number of facets of the n-th multiplihedron.
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LINKS
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FORMULA
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G.f.: x^2*(2 - 4*x + x^2) / ((1 - x)^3*(1 - 2*x)).
a(n) = 5*a(n-1) - 9*a(n-2) + 7*a(n-3) - 2*a(n-4) for n>4.
(End)
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PROG
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(PARI) a(n) = n*(n-1)/2 + 2^(n-1) - 1;
(PARI) concat(0, Vec(x^2*(2 - 4*x + x^2) / ((1 - x)^3*(1 - 2*x)) + O(x^40))) \\ Colin Barker, Jun 10 2020
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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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STATUS
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approved
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