void setup() {
  // put your setup code here, to run once:
  pinMode(13, OUTPUT);
  pinMode(12, OUTPUT);
  //seed the LFSR with an initial 1 bit:
  digitalWrite(12, HIGH);
  digitalWrite(13, HIGH);
  while(millis() < 3); 
  digitalWrite(13, LOW);
  digitalWrite(12, LOW);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(13, millis() & 0x100 ? HIGH : LOW);
}