subroutine dbesks(xnu,x,nin,bk)
c***begin prologue  dbesks
c***date written   770601   (yymmdd)
c***revision date  820801   (yymmdd)
c***category no.  c10b3
c***keywords  bessel function,double precision,fractional order,
c             modified bessel function,sequence,special function,
c             third kind
c***author  fullerton, w., (lanl)
c***purpose  computes a d.p. sequence of modified bessel functions of
c            the third kind of fractional order.
c***description
c
c dbesks computes a sequence of modified bessel functions of the third
c kind of order xnu + i at x, where x .gt. 0, xnu lies in (-1,1),
c and i = 0, 1, ... , nin - 1, if nin is positive and i = 0, 1, ... ,
c nin + 1, if nin is negative.  on return, the vector bk(.) contains
c the results at x for order starting at xnu.  xnu, x, and bk are
c double precision.  nin is an integer.
c***references  (none)
c***routines called  d1mach,dbskes,xerror
c***end prologue  dbesks
      double precision xnu, x, bk(1), expxi, xmax, d1mach
      data xmax / 0.d0 /
c***first executable statement  dbesks
      if (xmax.eq.0.d0) xmax = -dlog (d1mach(1))
c
      if (x.gt.xmax) call xerror ( 'dbesks  x so big bessel k underflows
     1', 36, 1, 2)
c
      call dbskes (xnu, x, nin, bk)
c
      expxi = dexp (-x)
      n = iabs (nin)
      do 20 i=1,n
        bk(i) = expxi * bk(i)
 20   continue
c
      return
      end