function [pn1]=pn(n,tb)
g1=[0,0,0,0,0,0,1];
n1=2^n-1;
pn2=zeros(1,n1);
for i=1:1:n1
    p1=xor(g1(1,6),g1(1,7));
    pn2(1,i)=g1(1,7);
     for k=7:-1:2
         g1(1,k)=g1(1,k-1);
     end
     g1(1,1)=p1;
 end
 t1=tb:tb:tb*n1;
 figure
 stairs(t