Sum of consecutive integers

some notes

% use while conecutive to compute sum of consecutive integers
clear;clc;
start = input('Enter the first value: ');
last = input('Enter the last value: ');
if start < last
    i=1;
    series=[start:1:last];
    diff = last - start;
    sum(i) = series(i);
    while i<(diff+1)
        i=i+1;
        sum(i) = series(i-1)+series(i);
    end
elseif start == last
    sum = start;
else
    i=1;
    series = [start:-1:last];
    diff = start -last;
    sum(i) = series(i);
    while i <(diff+1)
        i=i+1;
        sum(i) = series(i-1)+series(i);
    end
end
disp(sum);

output

>>Enter the first value: 20
Enter the last value: 30
    20    41    43    45    47    49    51    53    55    57    59

>>Enter the first value: 20
Enter the last value: 20
    20


>>Enter the first value: 30
Enter the last value: 20
    30    59    57    55    53    51    49    47    45    43    41