const int sizeOFarray = 5;
int b[5] = {10, 20, 30, 40, 50};

void setup ()
  {
    Serial.begin(9600);
    for ( int i = sizeOFarray - 1; i >= 0; i--)
      {
        Serial.print("b[");
        Serial.print(i);
        Serial.print("]");
        Serial.print(" ");
        Serial.print(b[i]);
        Serial.print(" "); 
        Serial.println(b[i]*b[i]);
      }
  }
void loop () {}