Kurczaniedziala?

void setup() {
  for (int i = 2; i <= 13; i++){
    pinMode(i, OUTPUT);
    digitalWrite(i, HIGH);
  }
}
const int interval = 1000;
unsigned long prevMillis = 0;
int ls = LOW;
int i = 0;
void loop() {
  unsigned long currentMillis = millis();
  i = i%3;
  digitalWrite(11+i, LOW);

  if(prevMillis - currentMillis >= interval){
    prevMillis = currentMillis;
    digitalWrite(11+i, HIGH);
    i++;
  }
}