{1,2,3}has 1 seq， {1,2,3,4}have 3 seq

public int numberSequ(int[] arr){
  if(arr==null||arr.length<3)
   return 0;
 int sum = 0; 
 int count = 0;
for(int i=2; i<arr.length;i++){
  if(arr[i]-arr[i-1]==arr[i-1]-arr[i-2]){
    count++;
    sum = sum+count;
  }
else{
   count = 0;
 }
 }return sum;
}