I need to find a formula for this data set:

f(3) = 1

f(2) ~ .7

f(1) ~.57

f(0) = 0

the ~ indicates an approximate value (it does not need to be exact, just close to that value). The formula f(x)=(x^2+10)/19 works well for f(1:3), but it does not go to zero like I need. Can anyone give me a better formula to fit this data?