I'm trying to alternatively have a random int generate a binary number with 4 lights.

This is my current code, However, it seems that all the lights(leds) go on, I don't think the minus option works. As in, it won't take a value from the currently randomized digit. (randombinary = randombinary - x)

I also tried just "randombinary - x"

const int button = 2;
const int redone = 13;
const int redtwo = 8;
const int greenone = 12;
const int greentwo = 7;
int randomnumber = 0;
int randombinary = 0;


void setup() {

  pinMode(13, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(2, INPUT);

}
  void loop() {

delay(1000);

  int randomnumber = (1, 15);
  randombinary = randomnumber;

  if (randombinary >=8){
    digitalWrite(redone, HIGH);
   randombinary = randombinary - 8;
  }
 else {
   digitalWrite(redone, LOW);
 }


  if (randombinary >=4){
    digitalWrite(greenone, HIGH);
   randombinary = randombinary - 4;
  }
  else {
    digitalWrite(greenone, LOW);
  }

  if (randombinary >=2){
    digitalWrite(redtwo, HIGH);
  randombinary =  randombinary - 2; 
  }
  else  {
    digitalWrite(greentwo, LOW);
  }

  if (randombinary >=1){
    digitalWrite(greentwo, HIGH);
  randombinary =  randombinary - 1;
  }
  else  {
    digitalWrite(greentwo, LOW);
  }


  }

Would appreciate any help!