HypgF1:

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   Computes the value of the hypergeometric function
   F(alpha,1;gamma,x)

   Examples are:
   arctanh(x)/x = F(1/2,1;3/2; x^2) = HypgF1(1/2,3/2, x^2)
   log(1+x)  /x = F(  1,1;  2;-x  ) = HypgF1(  1,  2,  -x)
   arctan(x) /x = F(1/2,1;3/2;-x^2) = HypgF1(1/2,3/2,-x^2)

   Since version 1.
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   Form:
   [F, n] = HypgF1( alpha, gamma, x )
   [F, n] = HypgF1( alpha, gamma, x, tol )
   [F, n] = HypgF1( alpha, gamma, x, tol, nMax )
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   ------
   Inputs
   ------
   alpha                 Argument
   gamma                 Argument
   x                     Argument
   tol                   Tolerance (default 1.e-8);
   nMax                  Maximum number of iterations

   -------
   Outputs
   -------
   F                     Value of fraction
   n                     Number of iterations

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   References: Battin, R. H., An Introduction to the Mathematics and
                 Methods of Astrodynamics, AIAA, 1987, pp. 34-68.
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