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A146311 a(n) = cos(2*n*arcsin(sqrt(3)) = (-1)^n*cosh(2*n*arcsinh(sqrt(2)). 25
1, -5, 49, -485, 4801, -47525, 470449, -4656965, 46099201, -456335045, 4517251249, -44716177445, 442644523201, -4381729054565, 43374646022449, -429364731169925, 4250272665676801, -42073361925598085, 416483346590304049 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Apart from sign, same as A001079 (see first formula).

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (-10,-1).

FORMULA

a(n) = (-1)^n * A001079(n).

From Colin Barker, Oct 26 2014: (Start)

a(n) = ((-5-2*sqrt(6))^n + (-5+2*sqrt(6))^n)/2.

a(n) = -10*a(n-1)-a(n-2).

G.f.: (5*x+1) / (x^2+10*x+1).

(End)

MATHEMATICA

Table[Round[N[Cos[2 n ArcSin[Sqrt[3]]], 50]], {n, 0, 100}]

CoefficientList[Series[(5*x + 1)/(x^2 + 10*x + 1), {x, 0, 50}], x] (* G. C. Greubel, Jul 02 2017 *)

PROG

(PARI) Vec((5*x+1)/(x^2+10*x+1) + O(x^100)) \\ Colin Barker, Oct 26 2014

CROSSREFS

Cf. A001079.

Sequence in context: A155629 A096596 A001079 * A212818 A195206 A081474

Adjacent sequences:  A146308 A146309 A146310 * A146312 A146313 A146314

KEYWORD

sign,easy

AUTHOR

Artur Jasinski, Oct 29 2008

EXTENSIONS

a(18) from Colin Barker, Oct 26 2014

STATUS

approved

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Last modified March 2 06:48 EST 2021. Contains 341744 sequences. (Running on oeis4.)