Evaluating a recurring series in Octave using a while loop

Question

I'm trying to evaluate the series ∑^∞_n=1 u_n in Octave, using a while loop. The recurrence relation u_n+1 = (u_n)² is provided.

The summation should stop when |u_n| < 10^-8.

So far this is what I got:

n=30
ser(1)=0.5;
sumser(1)=ser(1)
for k=1:n
    ser(k+1)=ser(1)^2;
end
for k=1:n
    while sumser(k)<10^-8
        sumser(k+1)=sumser(k)+ser(k+1)
    endwhile
end

I keep getting the error:

error: addex: A(I): index out of bounds; value 2 out of bound 1

error: called from

addex at line 8 column 3

Answer 1

If I've understood your problem correctly, then this should do the trick. There are too many problems with your code to address individually (unless I've misunderstood the question):

u(1) = 0.5;
S = u;
n = 1;
while (abs(u(n)) >= 10e-8)
    n = n + 1;
    u(n) = u(n-1)^2;
    S(n) = u(n) + S(n-1);
end