求系列 2, 8, 18, 32, 50, 的第 n 项。 . . .

给定一个整数N ，任务是找到序列的第 N 项

2,  8,  18,  32,  50, ….till N terms

例子：

Input: N = 4 
Output: 32

Input: N = 6
Output: 72

方法：

从给定的系列中，找到第 N项的公式-

1st term = 2 * 1 ^ 2 = 2

2nd term = 2 * 2 ^ 2 = 8

3rd term = 2 * 3 ^ 2 = 18

4th term = 2 * 4 ^ 2 = 32

.

.

Nth term = 2 * N ^ 2

给定系列的第 N项可以概括为-

T_N = 2 * N ^ 2

插图：

Input: N = 6
Output: 72
Explanation:
T_N= 2 * N ^ 2
    = 2 * 6 ^ 2
    = 72

以下是上述方法的实现 -

C++

// C++ program to implement
// the above approach
#include 
using namespace std;
 
// Function to return nth
// term of the series
int find_nth_Term(int n)
{
    return 2 * n * n;
}
 
// Driver code
int main()
{
    // Value of N
    int N = 6;
 
    // function call
    cout << find_nth_Term(N) <<
            end;
    return 0;
}

Java

// Java program for the above approach
import java.io.*;
import java.lang.*;
import java.util.*;
 
class GFG {
 
  // Function to return nth
  // term of the series
  static int find_nth_Term(int n)
  {
    return 2 * n * n;
  }
 
  // Driver code
  public static void main (String[] args)
  {
 
    // Value of N
    int N = 6;
 
    // function call
    System.out.println(find_nth_Term(N));
  }
}
 
// This code is contributed by hrithikgarg03188.

Python

# Python program to implement
# the above approach
 
# Find n-th term of series
# 2, 8, 18, 32, 50...
 
def nthTerm(n):
 
    return 2 * n * n;
 
# Driver Code
if __name__ == "__main__":
   
    # Value of N
    N = 6
     
    # function call
    print(nthTerm(N))
 
# This code is contributed by Samim Hossain Mondal.

C#

// C# program to implement
// the above approach
using System;
 
class GFG
{
 
  // Function to return nth
  // term of the series
  static int find_nth_Term(int n)
  {
    return 2 * n * n;
  }
 
  // Driver Code
  public static void Main()
  {
     
    // Value of N
    int N = 6;
 
    // function call
    Console.Write(find_nth_Term(N));
 
  }
}
 
// This code is contributed by sanjoy_62.

Javascript

       // JavaScript code for the above approach
 
       // Function to return nth
       // term of the series
       function find_nth_Term(n) {
           return 2 * n * n;
       }
 
       // Driver code
 
       // Value of N
       let N = 6;
 
       // function call
       document.write(find_nth_Term(N) + '<br>');
 
      // This code is contributed by Potta Lokesh
   

输出

72

时间复杂度： O(1)
辅助空间： O(1)