primes

//prime number generator

#include <Wire.h>
#include <Adafruit_MCP23017.h>
#include <Adafruit_RGBLCDShield.h>

Adafruit_RGBLCDShield lcd = Adafruit_RGBLCDShield();
unsigned long check = 2;
unsigned long found = 1;
unsigned long timeNow = 0;

void setup() {
  Serial.begin(57600);
  lcd.begin(16, 2);
  //while(!Serial);

}

void loop() {
  if (isPrime(check) == 1) {
    Serial.print(found);
    Serial.print(F("  "));
    Serial.println(check);
    found ++;
  }

  //if (check > 1000) {
   // while(1);
  //}


  if (millis() - timeNow > 1000) {
    lcd.setCursor (0, 0);
    lcd.print(F("found "));
    lcd.print(found);
    lcd.setCursor(0, 1);
    lcd.print(F("in "));
    lcd.print(millis() / 1000);
    lcd.print(F("s. "));
    lcd.print(check);
    timeNow = millis();
  }
  check ++;


}

int isPrime(unsigned long test) {
  for (unsigned long div = 2; div <= sqrt(test); div ++) {
    if ((test % div == 0)) {
      return 0;
    }
  }
  return 1;
}