Encuentra la suma de la serie ?3 + ?12 +……… hasta N términos

Dado un número n, la tarea es encontrar la suma de los primeros n términos de esta serie. A continuación se muestra la serie: 

Ejemplos: 
 

Input: n = 10
Output: 95.2628

Input: n = 5
Output: 25.9808

Esta serie puede ser vista como- 

A continuación se muestra la implementación requerida: 
 

// C++ implementation of above approach
#include <bits/stdc++.h>
#define ll long long int
using namespace std;
 
// Function to find the sum
double findSum(ll n)
{
 
    // Apply AP formula
    return sqrt(3) * (n * (n + 1) / 2);
}
// Driver code
int main()
{
    // number of terms
    ll n = 10;
 
    cout << findSum(n) << endl;
    return 0;
}

// Java implementation of
// above approach
import java.io.*;
 
class GFG
{
 
// Function to find the sum
static double findSum(long n)
{
    // Apply AP formula
    return Math.sqrt(3) * (n *
                    (n + 1) / 2);
}
// Driver code
public static void main (String[] args)
{
    // number of terms
    long n = 10;
     
    System.out.println( findSum(n));
}
}
 
// This code is contributed
// by inder_verma..

# Python3 implementation of above approach
 
#Function to find the sum
import math
def findSum(n):
    # Apply AP formula
    return math.sqrt(3) * (n * (n + 1) / 2)
 
# Driver code
# number of terms
if __name__=='__main__':
    n = 10
    print(findSum(n))
 
# This code is contributed by sahilshelangia

// C# implementation of
// above approach
using System;
 
class GFG
{
 
// Function to find the sum
static double findSum(long n)
{
    // Apply AP formula
    return Math.Sqrt(3) * (n *
                    (n + 1) / 2);
}
// Driver code
public static void Main ()
{
    // number of terms
    long n = 10;
     
    Console.WriteLine( findSum(n));
}
}
 
// This code is contributed
// by inder_verma..

<?php
// PHP implementation of above approach
 
// Function to find the sum
function findSum($n)
{
 
    // Apply AP formula
    return sqrt(3) * ($n * ($n + 1) / 2);
}
 
// Driver code
 
// number of terms
$n = 10;
 
echo findSum($n);
 
// This code is contributed
// by inder_verma
?>

<script>
// Javascript implementation of
// above approach
 
    // Function to find the sum
    function findSum( n)
    {
     
        // Apply AP formula
        return Math.sqrt(3) * (n * (n + 1) / 2);
    }
 
    // Driver code
      
    // number of terms
    let n = 10;
 
    document.write(findSum(n).toFixed(4));
 
// This code is contributed by 29AjayKumar 
</script>

95.2628

Complejidad temporal: O(1) desde que se realizan operaciones constantes

Espacio auxiliar: O(1) para espacio constante para variables