fit4<-Arima(fatturati, order=c(1,0,0), seasonal=c(1,1,0))
fit4
Series: fatturati
ARIMA(1,0,0)(1,1,0)[12]

Coefficients:
         ar1     sar1
      0.4749  -0.6135
s.e.  0.1602   0.1556

sigma^2 estimated as 4.773e+10:  log likelihood=-454.47
AIC=914.94   AICc=915.76   BIC=919.43
tsdisplay(residuals(fit4))
Box.test(residuals(fit4), lag=16, fitdf=4, type="Ljung")

    Box-Ljung test

data:  residuals(fit4)
X-squared = 10.15, df = 12, p-value = 0.6028
plot(fit4$x,col="red")
lines(fitted(fit4),col="blue")
Error in NextMethod(.Generic) : cannot assign 'tsp' to zero-length vector