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Tribonacci Number Java

In this section, we will learn what is Tribonacci number and also create Java programs to that calculates the Tribonacci number. The Tribonacci number program is frequently asked in Java coding interviews and academics.

Tribonacci Number

Tribonacci numbers are the same as Fibonacci numbers. We can get the Tribonacci number by adding the previous three terms. The first three terms are a(0) = a(1) = 0 and a(2) = 1. It is an OEIS sequence A000073.

By using these three terms, we can calculate the next Tribonacci number. The general formula for Tribonacci numbers is:

Tribonacci Number Example

First few Tribonacci numbers are 0, 0, 1, 1, 2, 4, 7, 13, 24, 44, 81, 149, 274, 504, 927, 1705, 3136, 5768, 10609, 19513, 35890, 66012, 121415, 223317, 410744, 755476, 1389537, 2555757, 4700770.

Algorithm

tribonacci(n):
Begin
   first := 0, second := 1, third := 1
   print first, second, third
   for i in range n - 3, do
      next := first + second + third
      print next
      first := second
      second := third
      third := next
   done
End

Tribonacci Number Java Program Using Recursion

TribonacciNumbers.java

public class TribonacciNumbers
{
//function to calculate Tribonacci number
    static int printTribRec(int n)
    {
        if (n == 2 || n == 0 || n == 1)
        //returns 0 if the user enter 0, 1, and 2nd term of the series
            return 0;
        if (n == 3)
            return 1;
        else
            //calculates and returns the next term of the series
            return printTribRec(n - 1) + printTribRec(n - 2) + printTribRec(n - 3);
    }
    //
    static void printTrib(int n)
    {
        //loop executes up to n times,means that the function called n times and prints the number
        for (int i = 1; i < n; i++)
            System.out.print(printTribRec(i)+" ");
    }
    //driver code
    public static void main(String args[])
    {
        int n = 10;
        //function calling
        printTrib(n);
    }
}

Output:

0 0 1 1 2 4 7 13 24 44 81 149 274 504 927 1705 3136 5768 10609

Hence, we can say that the terms generated by the Tribonacci series are called Tribonacci numbers.

Find Nth Number of the Tribonacci Series

NthTribonacciNumber.java

import java.util.*;   
public class NthTribonacciNumber
{  
//method to calculate Tribonnaci number
public static int tribonacciTerm(int n)   
{  
if (n < 3)   
return n;  
//initializing the first three terms of the Tribonnaci series so that we can calculate the next term
int a = 0, b = 1, c = 1, d;  
//in the while loop --> is not an operator. These are two separate operators, -- and >.  
//the conditional's code decrements n by 1, while returning n's original value not decremented value  
//after that compares the original value with 3 using the > operator
//more specifically we can write it as while ((n--) > 3)     
while (n-- > 3)     
{  
d = a + b + c;  
a = b;  
b = c;  
c = d;  
}  
return c;  
}  
public static void main(String args[])   
{  
Scanner sc = new Scanner(System.in);  
System.out.print("Enter the term: ");  
//reads an integer from the user   
int n=sc.nextInt();  
//function calling  
int ans=tribonacciTerm(n);   
System.out.println("The "+n+"th term of the Tribonacci series is: "+ans);  
}  
}  

Output:

Enter the term: 12
12th Tribonacci number is: 274

Next TopicBernoulli number in Java

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