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A014916
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a(1)=1, a(n) = n*4^(n-1) + a(n-1).
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11
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1, 9, 57, 313, 1593, 7737, 36409, 167481, 757305, 3378745, 14913081, 65244729, 283348537, 1222872633, 5249404473, 22429273657, 95443717689, 404681363001, 1710351420985, 7207909559865, 30297653743161, 127054676987449
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OFFSET
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1,2
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LINKS
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FORMULA
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MAPLE
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a:=n->sum (4^n-4^j, j=0..n): seq(a(n)/3, n=1..31); # Zerinvary Lajos, Dec 14 2008
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MATHEMATICA
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CoefficientList[Series[1/((1 - x)(1 - 4*x)^2), {x, 0, 40}], x] (* Vincenzo Librandi, Oct 23 2012 *)
LinearRecurrence[{9, -24, 16}, {1, 9, 57}, 30] (* Harvey P. Dale, Jul 25 2015 *)
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PROG
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(Magma) I:=[1, 9]; [n le 2 select I[n] else 8*Self(n-1)-16*Self(n-2)+ 1: n in [1..30]]; // Vincenzo Librandi, Oct 23 2012
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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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