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Text File  |  1993-10-16  |  181b  |  6 lines
  1. #    expandEi expands ei(n,x) into power series.
  2. #    See also: expand, expandGa, expandExp.
  3.  
  4. ei(n_,x_) := if(n>=1, -n*ei(n-1,x)+x^n*e^x,
  5.     if(n<-1, (-ei(n+1,x)+x^(n+1)*e^x)/(n+1)))
  6.