byte pins[] = {
  3, 4, 5, 6, 7
};

int s = sizeof(pins);

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

void loop() {
  for (int i = 0; i < s; i++) {
    for (int j = i; j < s; j++) {
      digitalWrite(pins[j], HIGH);
    }
    delay(100);
    for (int j = i; j < s; j++) {
      digitalWrite(pins[j], LOW);
    }
    delay(100);
  }
  delay(400);
}