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A136201
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a(n) = 2*a(n-1) + 4*a(n-2) - 6*a(n-3) - 3*a(n-4).
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1
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0, 0, 0, 1, 2, 8, 18, 53, 124, 328, 780, 1969, 4718, 11648, 28014, 68405, 164824, 400240, 965304, 2337409, 5640122, 13637336, 32914794, 79525973, 191966740, 463636600, 1119239940, 2702647921, 6524535782, 15753313808, 38031163398
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OFFSET
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0,5
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COMMENTS
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Based on a Pell recurrence.
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LINKS
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Table of n, a(n) for n=0..30.
Index entries for linear recurrences with constant coefficients, signature (2,4,-6,-3).
G. C. Greubel, Table of n, a(n) for n = 0..1000
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FORMULA
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A137255(n+1) - 2*A137255(n), same recurrence.
a(n) = (-A108411(n) + A001333(n))/4. - R. J. Mathar, Apr 01 2008
a(n) = (1/8)*(1+sqrt(2))^n + (1/8)*(1-sqrt(2))^n + (1/24)*3^(n/2)*(-3 - sqrt(3) - 3(-1)^n + (-1)^n*sqrt(3)). - Emeric Deutsch, Mar 31 2008
G.f.: x^3/(3*x^4 + 6*x^3 - 4*x^2 - 2*x + 1). - Alexander R. Povolotsky, Mar 31 2008
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MAPLE
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a:=proc(n) options operator, arrow: expand((1/8)*(1+sqrt(2))^n+(1/8)*(1-sqrt(2))^n+(1/24)*3^((1/2)*n)*(-3-sqrt(3)-3*(-1)^n+(-1)^n*sqrt(3))) end proc: seq(a(n), n=0..30); # Emeric Deutsch, Mar 31 2008
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MATHEMATICA
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LinearRecurrence[{2, 4, -6, -3}, {0, 0, 0, 1}, 50] (* G. C. Greubel, Feb 23 2017 *)
CoefficientList[Series[x^3/(1-2 x-4 x^2+6 x^3+3 x^4), {x, 0, 50}], x] (* Harvey P. Dale, Apr 21 2022 *)
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PROG
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(PARI) x='x+O('x^50); Vec(x^3/(3*x^4 + 6*x^3 - 4*x^2 - 2*x + 1)) \\ G. C. Greubel, Feb 23 2017
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CROSSREFS
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Sequence in context: A267638 A153335 A119853 * A058082 A005675 A054358
Adjacent sequences: A136198 A136199 A136200 * A136202 A136203 A136204
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KEYWORD
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nonn,easy
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AUTHOR
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Paul Curtz, Mar 16 2008
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STATUS
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approved
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