(PARI)
my(x='x+O('x^N),y=1,y1=0,N=1,
dn=1/(-2*t^2*x^4-(2*t^2+3*t)*x^3-(2*t+1)*x ^2+(2*t-1)*x+1));
而(n++,
y1=(2*x^2*y'*((-t^2+t)*x+(-t+1)+(t^2*x*2+(t^2+)*x+t)*y)+
(t*x^2+t*x)*y^2-(2*t^2*x^3+3*t*x*2+(-t+1)*x-1))*dn;
如果(y1==y,中断);y=y1;);年;
};
((1+x)*z-1)*(1+t*x)/((1-t+t*(1+x)*z)*x*z^2);
};