>> a=[1:6;7 8 9 1 2 3;2 4 6 7 9 1];
>> sum=[];
>> for i=1:2:5
sum=[sum a(:,i)+a(:,i+1) ];
end
>> sum
sum =
3 7 11
15 10 5
6 13 10
a =
1 2 3 4 5 6
7 8 9 1 2 3
2 4 6 7 9 1