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A174836
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a(n) = 1 + ((6*n-1)*2^n + (-1)^n)/3.
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0
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1, 4, 16, 46, 124, 310, 748, 1750, 4012, 9046, 20140, 44374, 96940, 210262, 453292, 972118, 2075308, 4412758, 9349804, 19748182, 41593516, 87381334, 183151276, 383079766, 799713964, 1666536790, 3467291308, 7203018070, 14942907052, 30959555926, 64066595500, 132428158294
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: 1/(1-x) + 1/(3*(1+x)) - 1/(3*(1-2*x)) + 8*x/(1-2*x)^2. [Richard Choulet, Apr 04 2010]
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PROG
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(PARI) a(n) = 1 + ((6*n-1)*2^n+(-1)^n)/3; \\ Michel Marcus, Feb 05 2019
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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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Fernando J. Ballesteros (fernando.ballesteros(AT)uv.es), Mar 30 2010
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EXTENSIONS
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STATUS
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approved
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