What is f(x) when eg x = 0, 1, 2, 3, 4, 5, 6, etc y = 0, 8, 12, 14, 15, 15.5, 15.75 etc (the y value at x =1 is arbitrary) ie each successive y value adds half the difference of the preceding 2 values. (It is effectively the inverse of a first order exponential decay where the y value halves at constant x intervals). But it doesn’t fit an exponential ....! Could it be a type of hyperbola? or polynomial? or both? or something else entirely? I have no decent curve fitting software and struggling to find this. Thank you!