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A198964
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a(n) = (7*9^n - 1)/2.
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4
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3, 31, 283, 2551, 22963, 206671, 1860043, 16740391, 150663523, 1355971711, 12203745403, 109833708631, 988503377683, 8896530399151, 80068773592363, 720618962331271, 6485570660981443, 58370135948832991, 525331223539496923
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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)+4.
a(n) = 10*a(n-1)-9*a(n-2), n>1.
E.g.f.: exp(x)*(7*exp(8*x) - 1)/2.
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MATHEMATICA
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CoefficientList[Series[(3 + x)/(1 - 10 x + 9 x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Jan 03 2013 *)
LinearRecurrence[{10, -9}, {3, 31}, 30] (* Harvey P. Dale, Oct 10 2017 *)
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PROG
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(Magma) [(7*9^n-1)/2: n in [0..20]];
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CROSSREFS
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KEYWORD
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nonn,easy,changed
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AUTHOR
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STATUS
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approved
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