That is if you did shiny hunt Rayquaza. I know its random and I've been shiny hunting it for ~200 SRs, probably more. I always like knowing the average or median of shiny hunts.
Average and median aren't the same thing. But for the average (or mean) value, it's 4,096 attempts for those that hunt without shiny charm, and 1,365 attempts for those that hunt with a shiny charm. The median is a bit lower than that due to how the geometric distribution works, don't feel like calculating it right now. The mode (most common exact number of attempts before a shiny) is 1.