byte leds[]={6,7,8}; 
byte i=0;    
int del=30;  

void setup() {
	for (i=0;i<=2;i++) { 
		pinMode(leds[i],OUTPUT); 
	} 
} 

void loop() { 
	for (i=0;i<2;i++) { 
		digitalWrite (leds[i],HIGH); 
		delay(del); 
		digitalWrite(leds[i+1],HIGH); 
		delay(del); 
		digitalWrite (leds[i],LOW); 
		delay(del*2); 
	} 
	for (i=2;i>0;i--) { 
		digitalWrite (leds[i],HIGH); 
		delay(del); 
		digitalWrite(leds[i-1],HIGH); 
		delay(del); 
		digitalWrite (leds[i],LOW); 
		delay(del*2); 
	} 
}





