Fibonacci: how many calls does each approach make?
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n    fib(n)                 naive calls    memo calls     table steps
10   55                     177            19             9
20   6765                   21891          39             19
30   832040                 2692537        59             29
40   102334155              331160281      79             39

naive calls = every call the recursion made (counted, not predicted).
memo calls  = the same recursion with a notebook: 2n-1 calls, because each F(k) is computed once.
table steps = additions in the bottom-up loop (n-1).