Factorial Series in Java (Series #7)

Factorial Series in Java

Question : Write a program to print the following series.

S = 2! + (2! + 3!) - (2! + 3! + 5!) + (2! + 3! + 5! + 7!)......... n terms

The above series is very easy to solve

Logic :-

• First input number of terms
• The nth term will contain 'n' number of terms (ex- if n = 2, then it will contain 2 terms i.e. (2! + 3!))
• calculate the nth term by first finding the first 'n' number of prime numbers
• Now, calculate factorial of each prime number
• Add the factorials of all the prime numbers
• Now if the nth term is odd and not the first then it will be a negative term
• else it will be a positive term
• Store the result in the variable accordingly
• Print the result

Note : To understand the program clearly watch this video : https://youtu.be/CRX9zDJYY4U

Program to print the Series Program :-

Program :-

import java.io.*;

import java.util.*;

class Series7

{

    public static void main(String args[])

    {

        Scanner in = new Scanner(System.in);

        int n,i,sum=0;

        System.out.println("Enter number of Terms : ");

        n= in.nextInt();

        for(i=1;i<=n;i++) //loop for calculating particular term

        {

            int j,p=2,s=0,c=0,x=1,a,f=1;

            while(x<=i) //loop for calculating sum of prime factorials

            {

                for(j=1;j<=p;j++)

                {

                    if(p%j==0)

                    {

                        c++;

                    }

                }

                if(c==2)

                {

                    for(a=1;a<=p;a++) //calculating factor of Prime number

                    {

                        f=f*a;

                    }

                    s=s+f; //storing sum of factorial of prime number

                    f=1;

                    p++;

                    x++;

                    c=0;

                }

                else

                {

                    p++;

                    c=0;

                }

            }// end of while loop

            if(i%2!=0 && i!=1) //calculating series

            {

                sum= sum-s;

            }

            else

            {

                sum= sum+s;

            }

        }// end of for loop

        System.out.println("Sum of Series : "+sum);

    }// end of main method

}//end of class

For Proper Understanding Watch the Video :-

Watch this video : Factorial Series in Java

All the best :)

Keep Learning :)