18. Write a program to read the number n using the Scanner class and print the Tribonacci series: 0, 0, 1, 1, 2, 4, 7, 13, 24, 44, 81 . . . and so on.

Hint: The Tribonacci series is a generalisation of the Fibonacci sequence where each term is the sum of the three preceding terms.

Java

import java.util.Scanner;
 
public class TribonacciSeries {
    public static void main(String[] args) {
 
        Scanner sc = new Scanner(System.in);
 
        System.out.print("Enter number of terms: ");
        int n = sc.nextInt();
 
        int a = 0, b = 0, c = 1;
        int next;
 
        System.out.print("Tribonacci Series: ");
 
        if (n >= 1)
            System.out.print(a + " ");
        if (n >= 2)
            System.out.print(b + " ");
        if (n >= 3)
            System.out.print(c + " ");
 
        for (int i = 4; i <= n; i++) {
            next = a + b + c;
            System.out.print(next + " ");
 
            a = b;
            b = c;
            c = next;
        }
    }
}

Output

Sample Input
Enter number of terms: 11
Sample Output 
Tribonacci Series: 0 0 1 1 2 4 7 13 24 44 81

📝 Explanation

First three terms are 0, 0, 1
Each next term is the sum of previous three terms
Values are shifted after every iteration

🔑 Logic Used

next = a + b + c

a = b

b = c

c = next