Another quickie today, a Kerry Mitchell formula with gif and jpg
at the usual http://maxitersfractalfollies.blogspot.com.
Also I finally got around to re-sampling the Aug. 16 post.

fract424.gif       { ; green tendrils
                     ; blank
                     ; calctime   0:12:31.88
                     ; created Sep 17, 2010
                     ;  Fractint Version 2004 Patchlevel 9
  reset=2004 type=formula formulafile=kerrym.frm
  formulaname=field3_man passes=1
  center-mag=-0.12869856067348150/+0.98735067767556690/237.828
  params=10000000/7 float=y maxiter=1500 inside=0 decomp=256
  periodicity=0
  colors=0100200300400500700800900A00B00D00E00F00G00H00J00K00L00M00N00P00Q\
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  0Qt0Ru0Su0Tu0Tu0Uv0Vv0Wv0Xw0Yw0Zw0Zx0_x0`x0ay0by0cy0dz1dz1ez1ez1fz2fz2gz\
  2gz2hz3hz3iz3iz3jz4jz4kz4kz4lz5mz5mz5nz5nz6oz6oz6pz6pz7qz7qz7rz7rz8sz8sz\
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  2ez2dz1dz1cz1bz1ay1`y1_y1_x1Zx1Yx1Xw1Ww1Vw1Uv1Uv1Tv1Su1Ru1Qu1Pt1Ot1Ot1Nt\
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  03J03I02H02G02F02E02D02C02B02A0190180170160150140130010
  }
frm:field3_man { ; Kerry Mitchell 20jan98
        ;
        ; Colors Mandelbrot set by nearest approach to
        ;   period 3 field lines
        ;
        ; use decomp=256
        ; real(p1) = bailout (try 1e12)
        ; imag(p1) = number of field line to use:
        ;   0, 1, 2, 3, 4, 5, 6, 7
        ; 3 iterations per pixel
        ; variable zc used for calculation, z for coloring
        ;
        zc=0, c=pixel, maxr=real(p1), minr=maxr, iter=1
        fieldangle=tan(imag(p1)*2*pi/7):
        ;
        ; iteration
        ;   compare tangent of polar angle with desired
        ;   field line angle, update minimum if needed
        ;
        iter=iter+3, zc=sqr(zc)+c, zc=sqr(zc)+c, zc=sqr(zc)+c
        rzc=|zc|, tanangle=imag(zc)/real(zc),
        r=cabs(fieldangle-tanangle)
        if (r<minr)
          minr=r
          end if
        ;
        ; bailout
        ;   set "iteration done" flag (iter=-1)
        ;   use log of minimum difference of angles as
        ;     decomposition angle
        ;
        if ((rzc>maxr)||(iter>=maxit))
          iter=-1
          angle=log(minr)
          z=cos(angle)+flip(sin(angle))
          end if
        iter>0
        }
Roger Alexander