int pinos = 0;
int tempo = 100;

void setup() {

  for (pinos=3; pinos < 13; pinos++) {
    pinMode(pinos , OUTPUT);
  }

}

void loop() {
  
  for (pinos=3; pinos < 13; pinos++) {
    digitalWrite(pinos, HIGH);
    delay(tempo);
  }  

  for (pinos=12; pinos > 2; pinos--) {
    digitalWrite(pinos, LOW);
    delay(tempo);
  }

}