output is NaN

[leeningli]

/*Geometric sequence
/
func PrepareTrainingData_dengbishulie(n int) [][][]float64 {
traindatas := make([][][]float64,0)
for i:=0;i<n;i++{
for j:=0;j<n;j++{
traindatas = append(traindatas,[][]float64{[]float64{float64(i),float64(j)},[]float64{float64(ij)}})
}
}
fmt.Printf("%++v",traindatas)
return traindatas
}

/main/
n,err := fonet.NewNetwork([]int{2, 1, 1},fonet.LeakyReLU)
if err != nil {
panic(err.Error())
}
trainingdata := PrepareTrainingData_dengbishulie(10)

n.Train(trainingdata,100,0.95,true)
fmt.Println(n.Predict([]float64{2,6}))

------output is NaN
why???