// https://www.arduino.cc/reference/en/language/structure/control-structure/for/

const int PWM_PIN = 6;

void setup() {
  Serial.begin(9600);
  Serial.println("Count up to 255 by 5");
  for (int i = 0; i <= 255; i += 5)  {
    Serial.println(i);
  }
  Serial.println("\nLogarithmic progression");
  for (int x = 2; x < 500; x = x * 1.5) {
    Serial.println(x);
    delay(100);
  }
  Serial.println("\nNow fade up and down forever...");
}

void loop() {
  ///*
  int x = 1;
  for (int i = 0; i > -1; i = i + x) {
    analogWrite(PWM_PIN, i);
    if (i == 255) {
      x = -1;  // switch direction at peak
    }
    delay(10);
  }
  //*/
}