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 A176458 Decimal expansion of 4+sqrt(17). 6

%I

%S 8,1,2,3,1,0,5,6,2,5,6,1,7,6,6,0,5,4,9,8,2,1,4,0,9,8,5,5,9,7,4,0,7,7,

%T 0,2,5,1,4,7,1,9,9,2,2,5,3,7,3,6,2,0,4,3,4,3,9,8,6,3,3,5,7,3,0,9,4,9,

%U 5,4,3,4,6,3,3,7,6,2,1,5,9,3,5,8,7,8,6,3,6,5,0,8,1,0,6,8,4,2,9,6,6,8,4,5,4

%N Decimal expansion of 4+sqrt(17).

%C Continued fraction expansion of 4+sqrt(17) is A010731.

%C This is the shape of an 8-extension rectangle; see A188640 for definitions. [_Clark Kimberling_, Apr 09 2011]

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Metallic_mean">Metallic mean</a>

%F a(n) = A010473(n) for n > 1.

%F Equals exp(arcsinh(4)), since arcsinh(x)=log(x+sqrt(x^2+1)). - _Stanislav Sykora_, Nov 01 2013

%e 4+sqrt(17) = 8.12310562561766054982...

%t r=8; t = (r + (4+r^2)^(1/2))/2; FullSimplify[t]

%t N[t, 130]

%t RealDigits[N[t, 130]][[1]]

%o (PARI) 4+sqrt(17) \\ _Charles R Greathouse IV_, Jul 24 2013

%Y Cf. A010473 (decimal expansion of sqrt(17)), A010731 (all 8's sequence).

%K cons,nonn

%O 1,1

%A _Klaus Brockhaus_, Apr 20 2010

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Last modified May 25 17:53 EDT 2020. Contains 334595 sequences. (Running on oeis4.)