#define BUTTON_PIN 13
#define LED1_PIN 3
#define LED2_PIN 5
#define LED3_PIN 8
boolean ledPatternActive = false;
int currentLED = LED1_PIN;
void setup() 
{
   pinMode(BUTTON_PIN, INPUT_PULLUP);
   pinMode(LED1_PIN, OUTPUT);
   pinMode(LED2_PIN, OUTPUT);
   pinMode(LED3_PIN, OUTPUT);
}
void loop() 
{
  if(digitalRead(BUTTON_PIN)==LOW)// put your main code here, to run repeatedly:
  {
    ledPatternActive = ! ledPatternActive;
    delay(500);
  }

if(ledPatternActive)
{
  digitalWrite(currentLED,HIGH);
  delay(500);
  digitalWrite(currentLED,LOW);
  currentLED=(currentLED == LED3_PIN) ? LED2_PIN : (currentLED + 1);
 }
}