int ledPin = 13;        // LED connected to pin 13
int delayTime = 100;   // Initial delay time in milliseconds

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
  Serial.println("LED Slow Flash Program Started");
}

void loop() {

  // LED ON
  digitalWrite(ledPin, HIGH);
  Serial.print("LED ON | Delay = ");
  Serial.print(delayTime);
  Serial.println(" ms");
  delay(delayTime);

  // LED OFF
  digitalWrite(ledPin, LOW);
  Serial.print("LED OFF | Delay = ");
  Serial.print(delayTime);
  Serial.println(" ms");
  delay(delayTime);

  // Increase delay
  delayTime = delayTime + 100;
}