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A125889
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Denominator of sum of first n ratios of Fibonacci to Lucas numbers.
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2
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1, 1, 3, 6, 42, 462, 1386, 40194, 1889118, 17946621, 735811461, 146426480739, 3367809056997, 1754628518695437, 493050613753417797, 30569138052711903414, 67466087682335170834698, 240921399113618895050706558, 77335769115471665311276805118
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OFFSET
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0,3
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COMMENTS
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GCD(F(i),L(i)) <= 2, so the ratio reduces when there is a factor of two in common, every third term. Example as continued fraction: 0 + 1 + 1/3 + 2/4 + 3/7 + 5/11 + 8/18 + 13/29 + 21/47 + 34/76 + 55/123 = 4 + 1/(1 + 1/(19 + 1/(4 + 1/(1 + 1/(13 + 1/(2 + 1/(4 + 1/(1 + 1/(6 + 1/(6 + 1/(1 + 1/(85 + 1/(1 + 1/(4 + 1/2)))))))))))))).
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LINKS
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FORMULA
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a(n) = denominator(Sum_{i=1..n} F(i)/L(i));
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EXAMPLE
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The fractions, reduced to lowest terms, begin: 0/1, 1/1, 4/3, 11/6, 95/42, 1255/462, 4381/1386, 145067/40194, 7662223/1889118, 80819870/17946621, 3642636055/735811461, ...
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MATHEMATICA
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With[{nn=20}, Join[{1}, Denominator[Accumulate[Fibonacci[Range[nn]]/ LucasL[ Range[ nn]]]]]] (* Harvey P. Dale, Mar 21 2015 *)
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PROG
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(Magma) [1] cat [Denominator(&+[Fibonacci(i)/Lucas(i): i in [1..n]]): n in [1..25]]; // Vincenzo Librandi, Mar 25 2017
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CROSSREFS
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KEYWORD
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easy,frac,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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