Table:
n=1→f(1)=4
n=2→f(2)=20
n=3→f(3)=100
Possible options with f(1)=4: Second and third. Let's check each one:
Second option:
f(1)=4
n=2→f(2)=5*f(2-1)=5*f(1)=5*4→f(2)=20=f(2) of the table.
n=3→f(3)=5*f(3-1)=5*f(2)=5*20→f(3)=100=f(3) of the table.
Third option:
f(1)=4
n=2→f(2)=16*f(2-1)=16*f(1)=16*4→f(2)=64 different to 20=f(2) of the table.
Answer: The recursive function that defines the sequence is the second option:
f(1)=4,
f(n)=5*f(n-1), for n>=2