int i;

void setup() {
	for (i=2;i<=9;i++) {
  	pinMode(i, OUTPUT);
	}
}

void loop() {
	for (i=2;i<=9;i++) {
  	digitalWrite(i, HIGH);
  	delay(100);
  	digitalWrite(i, LOW);
	}
	for (i=9;i>=2;i--) {
  	digitalWrite(i, HIGH);
  	delay(100);
  	digitalWrite(i, LOW);
	}
}