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A290124
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a(n) = a(n-1) + 12*a(n-2) with a(1) = 1 and a(2) = 2.
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0
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1, 2, 14, 38, 206, 662, 3134, 11078, 48686, 181622, 765854, 2945318, 12135566, 47479382, 193106174, 762858758, 3080132846, 12234437942, 49196032094, 196009287398, 786361672526, 3138473121302, 12574813191614, 50236490647238, 201134248946606, 803972136713462, 3217583124072734
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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a(n) = (5/28)*4^n - (2/21)*(-3)^n.
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MATHEMATICA
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CoefficientList[Series[(1 + x) / ((1 + 3 x) (1 - 4 x)), {x, 0, 33}], x] (* Vincenzo Librandi, Aug 27 2017 *)
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PROG
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(PARI) a(n) = if (n==1, 1, if (n==2, 2, a(n-1) + 12*a(n-2))); \\ Michel Marcus, Jul 25 2017
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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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