I have two loops which calls recursive function

for 1 to 9
  for 0 to 9
    ans+=f(n-2,j,i) // f(rem,prev,prev_prev)

function f(i,j,k) has dp[1001][10][10] memoized solution.why doesnt it timeout.
I'm having hard time understanding my own solution although it is ACd in one trial.