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A113836
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a(n) = Sum[2^(A001651(i-1)-1), {i,1,n}].
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3
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1, 3, 11, 27, 91, 219, 731, 1755, 5851, 14043, 46811, 112347, 374491, 898779, 2995931, 7190235, 23967451, 57521883, 191739611, 460175067, 1533916891, 3681400539, 12271335131, 29451204315, 98170681051, 235609634523
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OFFSET
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1,2
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COMMENTS
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For n>1: a(n)=A173593(3*n-5): terms of A173593 ending with digits '11' in binary representation;
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LINKS
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FORMULA
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Empirical g.f.: x*(2*x+1) / ((x-1)*(8*x^2-1)). - Colin Barker, Sep 01 2013
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EXAMPLE
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MATHEMATICA
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a = {}; s = 0; For[n = 1, n < 40, n++, If[Length[Intersection[{Mod[n, 3]}, {1, 2}]] > 0, s = s + 2^(n - 1); AppendTo[a, s]]]; a
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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