#define START_LED 2
#define LED_COUNT 8

uint8_t count = 0;

void setup() {
  Serial.begin(115200);

  for (uint8_t led = START_LED; led < LED_COUNT + START_LED; led++) {
    pinMode(led, OUTPUT);
  }
}

void loop() {
  setLEDsToCount();
  Serial.print("DEC: ");
  Serial.print(count,DEC);
  Serial.print(" BIN: 0b");
  Serial.print(count,BIN);
  Serial.print(" HEX: 0x");
  Serial.println(count,HEX);
  delay(1000);
  count++;
}

void setLEDsToCount() {
  for (uint8_t led = START_LED; led < LED_COUNT + START_LED; led++) {
    if ((count >> led - START_LED) & 0x1) {
      digitalWrite(led, HIGH);
    } else {
      digitalWrite(led, LOW);
    }
  }
}