calculate PI by Leibniz

/*
 * Calculate PAI by Leibniz infinite number serie
 * 3.141592653589793238462643383279502884197169399375105820974944592307816406286 ...
 * The program sums with each loop the result of 4*[(-1)^(n+1)]/(2*n-1)
 * to the value of pai
 *
 */
float pai = 0; // the calculated value
float oddNum = 1; // the value of the nominator
int sign = 1;// the sign of the current sum

void setup() {
  Serial.begin(9600);
}

void loop() {
  pai = pai + 4 * sign / oddNum;
  sign = -sign;
  oddNum = oddNum + 2;
  Serial.println(pai,10);

}