#define LED 9
int i ;
void setup() 
{
 pinMode(LED, OUTPUT);
}
void loop()
{
  for(i=0; i<=255; i+=25)
 { 
  analogWrite(LED, i);
  delay(1000);
 }
 for(i=255; i>=0; i-=51)
 {
  analogWrite(LED, i);
  delay(2000); 
 }
}