MATLAB: Sum digits of big numbers

sum digits

Hi,
I'm trying to solve the following problem:
for a^b when 0 < a,b < 100 I want to find the maximum sum of digits of the generated numbers. For example 9^3=729, sum=7+2+9=18.
I have the following code:
clear all
clc
digits(1000)
tot=0;
for a=99:-1:1 
    for b=99:-1:1  
        Num=vpa(sym(a^b));
        dig=double(1+floor(log10(Num)+eps));      
        Num=Num/10^dig;
        sumA=0;
        for i=1:dig+1
            sumA = sumA+(floor(Num*(10^(i-1)))-10*floor(Num*10^(i-2)));
        end
        temp=double(sumA);        
        if temp == 972           
           disp(a)
           disp(b)
        end              
    end
end
Where I found that 88^99 yields the max sum of digits 978, but it's the wrong answer. (correct answer is 972). Does anyone find the error?
Cheers!

Best Answer

Does sym(a^b) reply a symbolic variable? I'd assume, that at first a^b is calculated as double with the corresponding rounding errors. What about sym('a^b')? I do not have the required toolbox, such that this is a guessing only.
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