Find a recursive rule for the sequence 3, 6, 12, 24, …

Question

I can't decide if it's

a sub n= (2)n times sub n-1

or

a sub n= 1/2 times sub n-1

Answer 1

first, you might fix your typos. Your formulas are bogus.

Next, you can easily see that the values get bigger and bigger, so the 1/2 formula can't be right.

Your first try is right, but should be written

a(1) = 3
a(n) = 2*a(n-1) for n > 1