add element from for list to array

i have

a=[ 2 6 9 15]
s=0;
for i=1:7
s=s+a(i);
k=s
end

know i want my result will be [0 2 8 17]

but for my code my result is

                             k=2;
                             k=8
                             k=17

but i want it will be lik above not like this please help

[Walter Roberson]

duplicates http://www.mathworks.co.uk/matlabcentral/answers/107099-add-numbers-to-array