Here is another version of the Collatz fractal using complex numbers. I found some images on this link and a simpler formula than the one on Wikipedia (both give the same image though): https://yozh.org/2012/01/12/the_collatz_fractal/ Here is the PAR: Collatz2 { ; Exported from Fracton. reset=2004 type=formula formulafile=fracton.frm formulaname=F_20211202_1537 passes=1 float=y center-mag=0/0/0.3809523857142857/1/0/0 params=0/0/0/0/0/0/0/0/0/0 maxiter=1000 inside=1 proximity=0 colors=000FLQQvgz`6`KP1vWH1zpVDeg86Zw`_w4hpK7pGHze\ pdkSSP8ZQj5HMDPjRg`CG6RtBZ8Re_jOCrWSUAGRKbetEe`DdF\ NJPhm_f9XSn`ehRV5g1WdcfHO8ryINGfDR1hE3KpG`ZfoqpnKT\ gXD_0ys7ZP7EnbS2ssyO`uCz4UuAhCWvvB0NGZiXnWL3rhl`_p\ PGVG5Jn0HGN6IIuCEqxRMQSCrHziJSMy08YJZ_P_tu94idZBBY\ 9`5LYhHYmTYxL`T7k79IqpR9PhG3aZNgK`AHRbjerpMRLhZ4gH\ GTNl57UigYV_NE_affhn7joo05yIDWQxEVQfnGkqH5WJxmSLeS\ GVqzJUC9c3VfVyEGlC89cyabbd2h27zwDE5sywwkQ_dX2cN5TH\ EaYzfzaLb2wnTxxtZ5VRh1HFzfcrbkiEwdrvs30wtYJqjkBgeR\ YFMzpH2XRBqWAdkU5q1a8pAciLP2n9U0ni3gZjR63cp2YXjXcu\ FN2GtWNpuz08b51LU6dWv9esETy5fPzO81_Ef0sZaDIoT7vba6\ 3JT8uBZPmwvucYcFKbGfUHhlLkvlFAp`Xd5E2KHsb3Z76m5ad9\ WonMODBkdxjdyNYtzIfgfQKdDErbFehLRN7gcV30pjDqCFOGXs\ 7J1x2KCeVZCvNXDz8oN3VzOQQa3v4jAJ2dPuB0U4XFVrJv954o\ PlI_oSCoY7ODXVhrm8RvcIYP2rwYdhgNQyWtKXMVzRuLNAtf5w\ heuN6l6JUDLdJeyUSRdZjg9Uy } frm:F_20211202_1537 { ; Collatz fractal z=pixel: ; Wikipedia formula commented out but gives same result ;cz = cos(z * pi / 2); ;sz = sin(z * pi / 2); ;z = (z / 2) * cz * cz + sz * sz * (3 * z + 1); z=(2+7*z-(2+5*z)*cos(pi*z))/4, |z|<100 } -- Mike Frazier www.fracton.org