function [vec] = pkvece(v,k,e)


if k==1
    vec = [v(1)];
   
    return
elseif k==2 
    vec = [v(1),(v(1)*v(2)-1];
    return
else
    pk1 = pkvec(k-1,v);
    vec = [pk1, (pk1(k-1))*v(k)-pk1(k-2)];
end;


end
