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A156590 Decimal expansion of the imaginary part of the limit of f(f(...f(0)...)) where f(z)=sqrt(i+z). 5

%I #14 Jun 18 2015 05:56:48

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

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

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

%N Decimal expansion of the imaginary part of the limit of f(f(...f(0)...)) where f(z)=sqrt(i+z).

%C The real part, 1.300242590..., is given by A156548.

%C Coincides with the limit of the imaginary part of the same expression, but with f(z)=i/(1+z), and therefore with the imaginary part of the continued fraction i/(1+i/(1+i/(...))). It is also equal to the real part of the continued fraction i/(i+i/(i+i/(...))). - _Stanislav Sykora_, May 27 2015

%F Define z(1)=f(0)=sqrt(i), where i=sqrt(-1), and z(n)=f(z(n-1)) for n>1.

%F Write the limit of z(n) as a+bi where a and b are real. Then a=(b+1)/(2b), where b=sqrt((sqrt(17)-1)/8).

%e 0.6248105338...

%t RealDigits[Sqrt[(Sqrt[17]-1)/8],10,120][[1]] (* _Vaclav Kotesovec_, May 28 2015 *)

%Y Cf. A156548.

%K nonn,cons

%O 0,1

%A _Clark Kimberling_, Feb 12 2009

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