Question

Write a recursive function program to find the nth element in the following arithmetic numerical sequence: 3, 11, 27, 59, 123, ...

Answer 1

following are the code in c++

#include<bits/stdc++.h>

using namespace std;

//fuction to find nth term of the sequence

int val(int n){

  if(n==1){

      return 3;

  }else{

      return val(n-1)+8*pow(2,n-2);

  }

}

// driver fuction

int main(){

  int n;

  cout << "Which element of the sequence would you like to know?\n";

cin >> n;

//checking for input less than 1

do{

   if(n<1)

   {

   cout<<"Please enter a  number greater than 0:"<<endl;

   cin>>n;

   }

}while(n<1);

//printing the output

cout<<n<<"th element of the sequence is: ";

cout << val(n);

}

Explanation:

in the given code, if user enter input less than 1 then it will again ask for the input greater than 0 . When the input is greater than 0,it calls the recursive function  with the parameter n .if the input is 1 then function will give 3 as output. And when input is greater than 1, the recursive function will return nth element of the given sequence.

output

which element of the sequence would you like to know?                                                                      

-1                                                                                                                          

Please enter a  number greater than 0:                                                                                      

0                                                                                                                          

Please enter a  number greater than 0:                                                                                      

5                                                                                                                          

5th element of the sequence is: 123