Is this acceptable in recursive formulas?

[Cloudless]

Say for the recursive formula 2, 5, 9, 19 , 37...Instead of writing it as a_n = a_n-1 + * 2 a_n-2

can you write it as:

a_n = 2a_n + (-1)ⁿJust double checking. I encountered this earlier helping someone and I haven't done recursive formulas in a while..

 

[AlephZero]

I think you meant a_n = 2a_n-1 + (-1)ⁿ

Sure. Your formula is the same as

a_n = a_n-1 + (-1)ⁿ + a_n-1
= a_n-1 + (-1)ⁿ + 2a_n-2 + (-1)^n-1
= a_n-1 + 2a_n-2