int led1_pin = 13;
int led2_pin = 9;

unsigned long st1; // started time for led 1
unsigned long st2; // started time for led 2
unsigned long ct;  // current_time

bool led1_state = HIGH;
bool led2_state = HIGH;

void setup() {
  pinMode(led1_pin, OUTPUT);
  pinMode(led2_pin, OUTPUT);
}

void loop() {
  ct = millis();

  if (ct - st1 > 2000) {
    led1_state = !led1_state;
    st1 = ct;
  }

  if (ct - st2 > 3000) {
    led2_state = !led2_state;
    st2 = ct;
  }

  digitalWrite(led1_pin, led1_state);
  digitalWrite(led2_pin, led2_state);
}