各位大神，论文修改意见让提供时间序列的数学表达式，只会做不会写公式啊，请教高手公式和公式表述。R结果如下：
> arima(bts, order = c(1,0,0),
+       seasonal = list(order = c(2,1,1)))

Call:
arima(x = bts, order = c(1, 0, 0), seasonal = list(order = c(2, 1, 1)))

Coefficients:
         ar1    sar1     sar2     sma1
      0.3946  0.0477  -0.4625  -1.0000
s.e.  0.0954  0.1028   0.1088   0.1405

sigma^2 estimated as 12.45:  log likelihood = -276.69,  aic = 563.37