I wonder about the source of the formula at internet
http://www.pantheory.org/HF.htm :
[((z+1)2-1) / ((z+1)2+1)] c / H0
H0 – Hubble’s constant, c – speed of light.
“Comparing Hubble calculated distances and brightnesses with Pan Theory calculations of distances and brightnesses."
I have checked the formula against 100 galaxies with [0