Exponential Decay formula would work.
is the remaining amout of material of the decay cycle is complete.
If you start with 100 grams of x this is your
If your decay rate is 2% this is your r.
If you do 1 second increments that would be your t.
The remaining amount becomes your new initial amount and you
Initial Amount Time Decay Rate Remaining Amount
100 grams 1 sec 2% 98.0198673307 grams
96.0789438852 grams 1 sec 2% 94.1764532455 grams
94.1764532455 grams 1 sec 2% 92.3116344834 grams
92.3116344834 grams 1 sec 2% 90.4837411776 grams
It would take 230.258509299 seconds to only have 1 gram of material left.
Actual examples of academic research, you can find at Exponential decay--Applications and examples
Edit: In my opinion another way of calling what you want would be a non-stochastic iterative time series.