Find f(5) for this sequence:
(I need the answer/how you got it so I can use it as a example for other problems)
f(1) = 2 and f(2) = 3, f(n) = f(1) + f(2) + f(n - 1), for n 2.

f(5) = ______

Question

Find f(5) for this sequence: 
(I need the answer/how you got it so I can use it as a example for other problems)
f(1) = 2 and f(2) = 3, f(n) = f(1) + f(2) + f(n - 1), for n > 2.

f(5) = ______

anonymous · Answer

f(5) = f(1) + f(2) + f(5-1) ? 
if so, f(5) = 2 + 3 + f(4) 
f(4) = f(1) + f(2) + f(4-1) = 2 + 3 + f(3)
f(3) = f(1) + f(2) + f(3-1) = 2 + 3 + 3
therefore f(5) = 2 + 3 + (2 + 3 + (2 + 3 + 3)) = 5 + 5 + 8 = 18
(assuming it's a recursive function)