求系列 1^2, (1^2+2^2), (1^2+2^2+3^2), .... 的 N 项之和

给定一个正整数N 。找到系列的前N 项的总和-

1², (1²+2²), (1²+2²+3²),….,till N terms

例子：

Input: N = 3

Output: 20

Input: N = 1

Output: 1

方法：使用以下模式形成序列。对于任何值 N-

S_N = N * (N+1)² * (N+2) / 12

下面是上述方法的实现：

C++

// C++ program to implement
// the above approach
 
#include 
using namespace std;
 
// Function to return sum of
// N term of the series
 
int findSum(int N){
  
  return N*(N+1)*(N+1)*(N+2)/12;
   
}
 
// Driver Code
 
int main()
{
    int N = 3;
     
    cout << findSum(N);
}

Java

// Java program to implement
// the above approach
 
class GFG {
 
    // Function to return sum of
    // N term of the series
 
    static int findSum(int N) {
 
        return N * (N + 1) * (N + 1) * (N + 2) / 12;
 
    }
 
    // Driver Code
 
    public static void main(String args[]) {
        int N = 3;
 
        System.out.print(findSum(N));
    }
}
 
// This code is contributed by Saurabh Jaiswal

Python3

# Python 3 program for the above approach
 
# Function to return sum of
# N term of the series
 
def findSum(N):
   
  return N*(N+1)*(N+1)*(N+2)//12
 
 
# Driver Code
if __name__ == "__main__":
   
    # Value of N
    N = 3   
    print(findSum(N))
 
# This code is contributed by Abhishek Thakur.

C#

// C# program to implement
// the above approach
using System;
class GFG
{
 
// Function to return sum of
// N term of the series
 
static int findSum(int N){
  
  return N*(N+1)*(N+1)*(N+2)/12;
   
}
 
// Driver Code
 
public static void Main()
{
    int N = 3;
     
    Console.Write(findSum(N));
}
}
 
// This code is contributed by Samim Hossain Mondal.

Javascript

// Javascript program to implement
// the above approach
 
// Function to return sum of
// N term of the series
 
function findSum(N){
  
  return N*(N+1)*(N+1)*(N+2)/12;
   
}
 
// Driver Code
 
let N = 3;
document.write(findSum(N));
 
// This code is contributed by Samim Hossain Mondal.

输出

20

时间复杂度：O(1)
辅助空间：O(1)