int val, leds[3] = {3,5,6};

void setup() {
  Serial.begin(9600);
  for (int i = 0; i < 3; i++) pinMode(i, OUTPUT);
}

void loop() {
  for (int i = 0; i < 3; i++) {
    val = random(255);
    analogWrite(leds[i], val);
    Serial.print(val);
    Serial.print(" ");
  }
  Serial.println("");
  delay(500);
}