int LEDPINS[] = {2, 3, 4, 5, 6, 7, 8, 9};

void setup()
{
  for (int i = 0; i < 8; i++)
  {
    pinMode(LEDPINS[i], OUTPUT);
  }
}

void loop()
{
  for (int i = 0; i < 8; i++)
  {
    digitalWrite(LEDPINS[i], HIGH);
    delay(300);
    digitalWrite(LEDPINS[i], LOW);
  }
}