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A016134
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Expansion of 1/((1-2x)(1-10x)).
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9
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1, 12, 124, 1248, 12496, 124992, 1249984, 12499968, 124999936, 1249999872, 12499999744, 124999999488, 1249999998976, 12499999997952, 124999999995904, 1249999999991808, 12499999999983616, 124999999999967232
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = 125*10^(n-2) - 2^(n-2) = a(n-1)*10 + 2^n. - Henry Bottomley, Jun 06 2000
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EXAMPLE
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G.f. = 1 + 12*x + 124*x^2 + 1248*x^3 + 12496*x^4 + 124992*x^5 + ...
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MATHEMATICA
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f[n_] := Sum[2^(k - 1)*10^(n - k), {k, n}]; Array[f, 18] (* Robert G. Wilson v, Dec 03 2016 *)
LinearRecurrence[{12, -20}, {1, 12}, 20] (* Harvey P. Dale, Jul 28 2020 *)
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PROG
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(Sage) [lucas_number1(n, 12, 20) for n in range(1, 18)] # Zerinvary Lajos, Apr 27 2009
(Sage) [(10^n - 2^n)/8 for n in range(1, 19)] # Zerinvary Lajos, Jun 05 2009
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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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