int n = 0;

void setup (){
  for (int i=4;i<=13;i++)
  pinMode (i, OUTPUT);

}
void loop () {
  for(int i=0;i<10;i++){
    if (int(n/pow(2,i))%2 == 0)
    digitalWrite(13-i,LOW);
    else
    digitalWrite(13-i,HIGH);
  }
  delay(100);
  n++;
}