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a(n) = cos(2*n*arcsin(sqrt(3)) ) = (-1)^n*cosh(2*n*arcsinh(sqrt(2))).
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G. C. Greubel, <a href="/A146311/b146311.txt">Table of n, a(n) for n = 0..1000</a>
a(n) = (-1)^n * A001079(n).
a(n) = ((-5-2*sqrt(6))^n + (-5+2*sqrt(6))^n)/2.
CoefficientList[Series[(5*x + 1)/(x^2 + 10*x + 1), {x, 0, 50}], x] (* G. C. Greubel, Jul 02 2017 *)
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<a href="/index/Rec#order_02">Index to sequences with entries for linear recurrences with constant coefficients</a>, signature (-10,-1).
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