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A087438
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a(n) = 3*2^(2*(n-1)) + 2^(n-2)*(n+1).
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1
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1, 4, 15, 56, 212, 816, 3184, 12544, 49728, 197888, 789248, 3151872, 12596224, 50360320, 201388032, 805437440, 3221504000, 12885491712, 51540852736, 206161051648, 824639225856, 3298546417664, 13194163650560, 52776608464896
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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G.f.: (1 - 4*x + 3*x^2)/((1-2*x)^2*(1-4*x)).
E.g.f.: (3*exp(4*x) + (1+2*x)*exp(2*x))/4.
a(n) = 8*a(n-1) - 20*a(n-2) + 16*a(n-3); a(0)=1, a(1)=4, a(2)=15. - Harvey P. Dale, May 20 2011
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MATHEMATICA
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LinearRecurrence[{8, -20, 16}, {1, 4, 15}, 30] (* or *) CoefficientList[ Series[ (1-4x+3x^2)/((1-2x)^2(1-4x)), {x, 0, 30}], x] (* Harvey P. Dale, May 20 2011 *)
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PROG
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(Magma) [3*2^(2*(n-1))+2^(n-2)*(n+1): n in [0..25]]; // Vincenzo Librandi, May 21 2011
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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