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  The Pin/ GPIO mapping or the numbering convention used by Arduino to address each GPIO pins is straightforward and it uses the actual pin position in the header of the Raspberry Pi. Obviously, pins used for power and GND can’t be used as GPIO but still, those pin numbers are not used for other GPIOs. Pin# defines the PIN no as used by Arduino.
  #include <SoftwareSerial.h> // SoftwareSerial mySerial(16, 15); int led=18; void setup() { Serial.begin(9600); for(int i=0;i<40;i++) pinMode(i, OUTPUT); Serial.println("Strating the application."); } void loop() { //Serial.println("Hello"); for(int i=1;i<14;i++){ digitalWrite(i, HIGH); delay(1000); digitalWrite(i, LOW); delay(1000); } }