int pins[] = {5,4,3,2,1,0};
int timeout = 100;

void led(int pin){
  digitalWrite(pin,HIGH);
  delay(timeout);
  digitalWrite(pin,LOW);
  delay(timeout);
}

void setup() {
  for(int i=0;i++;i<5){
    pinMode(pins[i],OUTPUT);
  }
}

void loop() {
  for(int i=0;i<6;i++){
    led(pins[i]);
  }
}