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A049440
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Fib(3n)^2 - 2*Fib(3n) + 4*Fib(3n+1) + 5.
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0
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9, 17, 105, 1313, 21385, 374833, 6688617, 119863873, 2150198793, 38580909137, 692294282601, 12422665840481, 222915477614473, 4000055027956849, 71778071199324777, 1288005210351490177
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OFFSET
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0,1
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COMMENTS
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Continued fraction for sqrt(a(n)) has period n.
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LINKS
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FORMULA
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G.f.: (-x^5 - 91*x^4 + 534*x^3 + 370*x^2 - 181*x + 9)/((x^2-18*x+1)*(x^2-1)*(x^2+4*x-1)) - Michael Somos.
a(n) = 22a(n-1) - 71a(n-2) - 36a(n-3) + 73a(n-4) + 14a(n-5) - a(n-6).
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MATHEMATICA
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#[[1]]^2-2#[[1]]+4#[[2]]+5&/@Table[{Fibonacci[3n], Fibonacci[3n+1]}, {n, 0, 20}] (* or *) LinearRecurrence[{22, -71, -36, 73, 14, -1}, {9, 17, 105, 1313, 21385, 374833}, 20] (* Harvey P. Dale, Jul 07 2017 *)
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CROSSREFS
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KEYWORD
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nonn,cofr
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AUTHOR
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STATUS
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approved
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