I've been using cryptocurrency revenue calculators and have appeared to figure out that for all of the major algorithms, the probability of a hash being valid is 1/(D*2^u) where u is either 0, 13 (weird), or 32 and D is the network difficulty. I used the formula (my_hashrateblock_rewardtime) * 1/D * 1/2^u to find revenue. I believe the following is true:
u = 32 for SHA-256, Scrypt, X11, Groestl, X11Ghost, Lyra2Rev2, NeoScrypt, Blake (14r)
u = 13 for Equihash
u = 0 for CryptoNight, Ethash
Can someone explain this phenomenon? Will the constant part of the probability change over time or will the difficulty adjust?