Trefoil2_3FourierKnot:

_FxGraph3D cos(2*u);cos(3*u + PI/4);cos(2*u + PI/2)+cos(u + PI/6);0;6.283185;0;0;200;0;1;0;1;UV

Note, there is a small space in the unclosed curve, locate-able by _MarkOpenCurveStart, or MarkCurveStart, or MarkCurveEnd script.
Trimming the curve with a point at say (0,-1,z), and blending the gap, will make a closed curve.

- Brian