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A128777
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a(n) = denominator of b(n): b(1)=2. b(n) be such that the continued fraction (of +-rational terms) [b(1);b(2),...,b(n)] = sum{k=1 to n-1} 1/b(k), for every integer n >= 2.
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1
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OFFSET
| 1,2
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COMMENTS
| This sequence is infinite if and only if b(n) does not equal -b(n+1) for every positive integer n.
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FORMULA
| For n >= 5, b(n) = - (b(n-1) + b(n-2)) * (b(n-2) + b(n-3)) /(b(n-1) * b(n-2)^2).
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EXAMPLE
| {b(k)} begins: 2, -2/3, 3, 7/3, -16/27, 141/49, -3023/768,...
So for example, 1/2 -3/2 + 1/3 = 2 + 1/(-2/3 +1/(3 + 3/7)) and 1/2 -3/2 + 1/3 + 3/7 = 2 + 1/(-2/3 +1/(3 + 1/(7/3 - 27/16))).
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CROSSREFS
| Cf. A128776.
Sequence in context: A197272 A160708 A040173 * A067009 A110790 A119719
Adjacent sequences: A128774 A128775 A128776 * A128778 A128779 A128780
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KEYWORD
| frac,more,nonn
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AUTHOR
| Leroy Quet Mar 27 2007
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