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A193579
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a(n) = 2*4^n + 7.
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2
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9, 15, 39, 135, 519, 2055, 8199, 32775, 131079, 524295, 2097159, 8388615, 33554439, 134217735, 536870919, 2147483655, 8589934599, 34359738375, 137438953479, 549755813895, 2199023255559, 8796093022215, 35184372088839, 140737488355335, 562949953421319, 2251799813685255
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OFFSET
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0,1
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COMMENTS
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LINKS
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FORMULA
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a(n) = 2^(2n + 1) + 7 = 3*(A020988(n) + 3).
G.f.: 3*(3 - 10*x)/((1 - x)*(1 - 4*x)).
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MATHEMATICA
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2*4^Range[0, 30]+7 (* or *) LinearRecurrence[{5, -4}, {9, 15}, 30] (* Harvey P. Dale, Jun 13 2020 *)
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PROG
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(PARI) Vec(3*(3 - 10*x)/((1 - x)*(1 - 4*x)) + O(x^20)) \\ Felix Fröhlich, Nov 07 2018
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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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