recursions.java

public class recursions{
    public static void main(String[] args) {
        int i = (int) (Math.random() * 51); // Example random input for the series from 0 to 50
        
        System.out.println("Sum of natural numbers up to " + i + " is: " + sumSeries(i));
        System.out.println("Harmonic series up to " + i + " is: " + harmonicSeries(i));
        System.out.println("Fraction series 1 up to " + i + " is: " + fractionSeries(i));
        System.out.println("Fraction series 2 up to " + i + " is: " + fractionSeries2(i));
    }
    public static int sumSeries(int i) {
        if (i == 1) {
            return 1;
        } else {
            return i + sumSeries(i - 1);
        }
    }

    public static double harmonicSeries (double i) {
        if (i == 1){
            return 1.0;
        }else {
            return 1.0/i + harmonicSeries(i-1);
        }
    }
    public static double fractionSeries (double i){
        if (i == 1){
            return 1.0/3;
        }else{
            return (double) i / (2 * i + 1) + fractionSeries(i - 1);
        }
    }
    public static double fractionSeries2(double i){
        if (i == 1){
            return 1.0/2;
        }else {
            return (double) i / (i + 1) + fractionSeries2(i - 1); 
        }
    }
}