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A163475
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a(n) = 18*a(n-1) - 78*a(n-2) for n > 1; a(0) = 3, a(1) = 30.
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3
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3, 30, 306, 3168, 33156, 349704, 3708504, 39476160, 421307568, 4504395744, 48217133088, 516565527552, 5537243115072, 59378264922240, 636903805624704, 6832763837309952, 73311252232852224, 786646960881163776
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OFFSET
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0,1
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COMMENTS
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LINKS
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FORMULA
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a(n) = ((3+sqrt(3))*(9+sqrt(3))^n + (3-sqrt(3))*(9-sqrt(3))^n)/2.
G.f.: (3-24*x)/(1-18*x+78*x^2).
E.g.f.: exp(9*x)*( 3*cosh(sqrt(3)*x) + sqrt(3)*sinh(sqrt(3)*x) ). - G. C. Greubel, Jul 26 2017
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MATHEMATICA
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LinearRecurrence[{18, -78}, {3, 30}, 50] (* G. C. Greubel, Jul 26 2017 *)
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PROG
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(Magma) [ n le 2 select 27*n-24 else 18*Self(n-1)-78*Self(n-2): n in [1..18] ];
(PARI) x='x+O('x^50); Vec((3-24*x)/(1-18*x+78*x^2)) \\ G. C. Greubel, Jul 26 2017
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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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