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A014131
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a(n) = 2*a(n-1) if n odd else 2*a(n-1) + 6.
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1
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0, 6, 12, 30, 60, 126, 252, 510, 1020, 2046, 4092, 8190, 16380, 32766, 65532, 131070, 262140, 524286, 1048572, 2097150, 4194300, 8388606, 16777212, 33554430, 67108860, 134217726, 268435452, 536870910
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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.: 6x/((1-2x)(1-x)(1+x)).
a(n) = 2^(n+2) - 3 - (-1)^n. (End)
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MATHEMATICA
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Table[2^(n+2)-3-(-1)^n, {n, 0, 40}] (* or *) CoefficientList[Series[6x/((1-2x)(1-x)(1+x)), {x, 0, 30}], x] (* Vincenzo Librandi, Apr 03 2012 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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