int Zeit = 130;

void setup() {
 for (int i = 2; i < 7; i=i+1) {
    pinMode(i, OUTPUT);
 }

}

void loop() {
  for (int i = 2; i < 7; i=i+1) {
    digitalWrite(i, HIGH);
    delay(Zeit);
    digitalWrite(i, LOW);
    delay(Zeit);
  }

  for (int i = 5; i >2; i=i-1) {
    digitalWrite(i, HIGH);
    delay(Zeit);
    digitalWrite(i, LOW);
    delay(Zeit);
  }
}