int led;

void setup() {
  Serial.begin(9600); // serielle Schnittstelle vorbereiten
  for ( int led = 2; led <= 7; led = led+1 ) {
    pinMode ( led, OUTPUT );
  }
}

void loop() {
  for ( int led = 2; led <= 7; led = led+1 ) {
    Serial.print ("Led: " );
    Serial.println ( led );
    digitalWrite(led, HIGH);
    delay(300);
    digitalWrite(led, LOW);
  }
  for ( int led = 6; led >= 3; led = led-1 ) {
    Serial.print ("Led: " );
    Serial.println ( led );
    digitalWrite(led, HIGH);
    delay(300);
    digitalWrite(led, LOW);
  }
}