找到系列 3, 8, 15, 24, 的第 n 项。 . .

给定一个整数N ，任务是找到序列的第 N项

3, 8, 15, 24, . . .till Nth term

例子：

Input: N = 5 
Output: 35

Input: N = 6
Output: 48

方法：

从给定的系列中，找到第 N 项的公式 -

1st term  = 1 (1 + 2) = 3

2nd term = 2 (2 + 2) = 8

3rd term =  3 (3 + 2) = 15

4th term =  4 (4 + 2) = 24

.

.

Nth term = N * (N + 2) 

给定系列的第 N 项可以概括为-

T_N = N * (N + 2)

插图：

Input: N = 5
Output: 35
Explanation:
T_N = N * (N + 2)
     = 5 * (5 + 2)
     = 35

以下是上述方法的实现 -

C++

// C++ program to find nth term
// of the series
#include 
using namespace std;
 
// Function to return nth term
// of the series
int find_nth_Term(int n)
{
    return n * (n + 2);
}
 
// Driver code
int main()
{
    // Find given nth term
    int N = 5;
 
    // Function call
    cout << find_nth_Term(N) << endl;
    return 0;
}

Java

// Java program to find nth term
// of the series
class GFG
{
 
  // Function to return nth term
  // of the series
  static int find_nth_Term(int n) { return n * (n + 2); }
 
  // Driver code
  public static void main(String args[])
  {
 
    // Find given nth term
    int N = 5;
 
    // Function call
    System.out.println(find_nth_Term(N));
  }
}
 
// This code is contributed by gfgking

Python

# Python program to find nth
# term of the series
 
# Function to return nth
# term of the series
def find_nth_Term(n):
 
    return n * (n + 2)
 
 
# Driver code
 
# Find given nth term
n = 5
 
# Function call
print(find_nth_Term(n))
 
# This code is contributed by Samim Hossain Mondal.

C#

// C# program to find nth term
// of the series
using System;
class GFG
{
 
  // Function to return nth term
  // of the series
  static int find_nth_Term(int n) { return n * (n + 2); }
 
  // Driver code
  public static int Main()
  {
 
    // Find given nth term
    int N = 5;
 
    // Function call
    Console.WriteLine(find_nth_Term(N));
    return 0;
  }
}
 
// This code is contributed by Taranpreet

Javascript

       // JavaScript code for the above approach
 
       // Function to return nth term
       // of the series
       function find_nth_Term(n) {
           return n * (n + 2);
       }
 
       // Driver code
 
       // Find given nth term
       let N = 5;
 
       // Function call
       document.write(find_nth_Term(N) + '<br>');
 
      // This code is contributed by Potta Lokesh
   

输出

35

时间复杂度： O(1)
辅助空间： O(1)