Thread: iterative equation function

hi, im trying to write a program to solve the equation
A(n) = 2A(n-1)-3A(n-2) for n>1.
A(0) = 1 and A(1) = 2.

I've already wrote a recursive program to solve it but am trying to get an iterative version to work. The code I am using for the iterative version is below:

Code:

int A(int n)
{	
	int a, b;

	a = n-1;
	b = n-2;

	if(a==0||b==0)
		a=1;
	if(a==1||b==1)
		a=2;
	while(a>0&&b>1)
	{
		n = 2*a-3*b;
	}

	return n;
}

I am not entirely sure where I am going wrong, but this code leads to an infinite loop of nothing, and I cannot come up with a way of iterating a and b to get the desired result. I have also tried while loops and nested for loops without much luck. If anyone can point me in the right direction, I'd be grateful.