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A198966
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a(n) = 8*9^n-1.
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3
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7, 71, 647, 5831, 52487, 472391, 4251527, 38263751, 344373767, 3099363911, 27894275207, 251048476871, 2259436291847, 20334926626631, 183014339639687, 1647129056757191, 14824161510814727, 133417453597332551, 1200757082375992967
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) = 9*a(n-1)+8. a(n) = 10*a(n-1)-9*a(n-2), n>1.
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MATHEMATICA
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CoefficientList[Series[(7 + x)/(1 - 10*x + 9*x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Jan 03 2013 *)
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PROG
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(Magma) [8*9^n-1: n in [0..20]]
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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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