 
      FUNCTION BESI1(X)
C***BEGIN PROLOGUE  BESI1
C***DATE WRITTEN   770401   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  C10B1
C***KEYWORDS  BESSEL FUNCTION,FIRST KIND,HYPERBOLIC BESSEL FUNCTION,
C             MODIFIED BESSEL FUNCTION,ORDER ONE
C***AUTHOR  FULLERTON, W., (LANL)
C***PURPOSE  Computes the hyperbolic Bessel function of first kind of
C            order one
C***DESCRIPTION
C
C BESI1(X) calculates the modified (hyperbolic) Bessel function
C of the first kind of order one for real argument X.
C
C Series for BI1        on the interval  0.          to  9.00000D+00
C                                        with weighted error   2.40E-17
C                                         log weighted error  16.62
C                               significant figures required  16.23
C                                    decimal places required  17.14
C***REFERENCES  (NONE)
C***ROUTINES CALLED  BESI1E,CSEVL,INITS,R1MACH,XERROR
C***END PROLOGUE  BESI1
 
 
