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A179556
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a(1) = 10; a(n) = a(n-1)*10 - 2^(n-2).
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1
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10, 99, 988, 9876, 98752, 987504, 9875008, 98750016, 987500032, 9875000064, 98750000128, 987500000256, 9875000000512, 98750000001024, 987500000002048, 9875000000004096, 98750000000008192, 987500000000016384, 9875000000000032768, 98750000000000065536
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OFFSET
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1,1
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COMMENTS
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79/80 = 0.9875.
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LINKS
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FORMULA
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a(n) = 12*a(n-1) - 20*a(n-2) for n > 2.
G.f.: -x*(21*x - 10)/((2*x - 1)*(10*x - 1)). (End)
E.g.f.: (79*exp(10*x) + 5*exp(2*x) - 84)/80. - Stefano Spezia, Mar 04 2023
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MATHEMATICA
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a[1] := 10; a[n_] := a[n] = 10 a[n - 1] - 2^(n - 2); Array[a@ # &, {20}] (* Michael De Vlieger, Oct 03 2015 *)
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PROG
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(PARI) Vec(-x*(21*x-10)/((2*x-1)*(10*x-1)) + O(x^30)) \\ Colin Barker, Oct 03 2015
(PARI) a(n) = if(n<2, 10, a(n-1)*10 - 2^(n-2));
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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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EXTENSIONS
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STATUS
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approved
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