function [y] =prim(a)
    x=1:a^2/4
    for i=2:a/2
        for j=2:a/2
            x(i*j)=0;
        end
    end
    x(1)=0;
    j=1;
    for i=1:a
        if(x(i)~=0) then
            y(j)=x(i)
            j=j+1;
        end
    end
    j=j-1;
endfunction