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A020873
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a(n) is number of cycles in Moebius ladder M_n.
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16
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2, 3, 7, 15, 29, 53, 95, 171, 313, 585, 1115, 2159, 4229, 8349, 16567, 32979, 65777, 131345, 262451, 524631, 1048957, 2097573, 4194767, 8389115, 16777769, 33555033, 67109515, 134218431, 268436213, 536871725, 1073742695, 2147484579, 4294968289, 8589935649
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OFFSET
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0,1
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COMMENTS
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For n >= 2, a(n+1) is the number of connected induced (non-null) subgraphs of the n-wheel graph. - Giovanni Resta, May 04 2017
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LINKS
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FORMULA
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a(n) = 2^n + n^2 - n + 1.
a(n) = 5*a(n-1) - 9*a(n-2) + 7*a(n-3) - 2*a(n-4).
G.f.: (2 - 7*x + 10*x^2 - 7*x^3)/((2*x - 1)*(x - 1)^3). (End)
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MATHEMATICA
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PROG
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(PARI) Vec((2-7*x+10*x^2-7*x^3) / ((2*x-1)*(x-1)^3) + O(x^50)) \\ Colin Barker, Aug 01 2015
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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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