Skip to content
Related Articles

Related Articles

Improve Article
Program to find nth term of the series 1 4 15 24 45 60 92
  • Last Updated : 16 Mar, 2021

Given a number n, the task is to find the nth term of the series 
 

1, 4, 15, 24, 45, 60, 91, 112, 153…..

 
where 0 < n < 100000000.
Examples: 
 

Input: n = 10
Output: 180

Input: n = 5
Output: 45

Approach: 
The idea is very simple but hard to recognise. 
If n is odd, the nth term will be [ ( 2 * ( n^2 ) ) – n ]. 
If n is even, the nth term will be [ 2 * ( (n^2) – n ) ].
 



Implementation:
 

C++




#include <stdio.h>
 
// function to calculate nth term of the series
long long int nthTerm(long long int n)
{
    // variable nth will store the nth term of series
    long long int nth;
 
    // if n is even
    if (n % 2 == 0)
        nth = 2 * ((n * n) - n);
 
    // if n is odd
    else
        nth = (2 * n * n) - n;
 
    // return nth term
    return nth;
}
 
// Driver code
int main()
{
    long long int n;
 
    n = 5;
 
    printf("%lld\n", nthTerm(n));
 
    n = 25;
    printf("%lld\n", nthTerm(n));
 
    n = 25000000;
    printf("%lld\n", nthTerm(n));
 
    n = 250000007;
    printf("%lld\n", nthTerm(n));
 
    return 0;
}

Java




// Java implementation of the above approach
 
class GFG
{
 
    // function to calculate nth
    // term of the series
    static long nthTerm(long n)
    {
        // variable nth will store the
        // nth term of series
        long nth;
     
        // if n is even
        if (n % 2 == 0)
            nth = 2 * ((n * n) - n);
     
        // if n is odd
        else
            nth = (2 * n * n) - n;
     
        // return nth term
        return nth;
    }
     
    // Driver code
    public static void main(String []args)
    {
        long n;
        n = 5;
        System.out.println(nthTerm(n));
     
        n = 25;
        System.out.println(nthTerm(n));
     
        n = 25000000;
        System.out.println(nthTerm(n));
     
        n = 250000007;
        System.out.println(nthTerm(n));
    }
}
 
// This code is contributed by Ryuga

Python3




# function to calculate nth term of the series
def nthTerm(n):
 
    # variable nth will store the nth
    # term of series
    nth = 0
 
    # if n is even
    if (n % 2 == 0):
        nth = 2 * ((n * n) - n)
 
    # if n is odd
    else:
        nth = (2 * n * n) - n
 
    # return nth term
    return nth
 
# Driver code
n = 5
 
print(nthTerm(n))
 
n = 25
print(nthTerm(n))
 
n = 25000000
print(nthTerm(n))
 
n = 250000007
print(nthTerm(n))
 
# This code is contributed by
# Mohit kumar 29

C#




// C# implementation of the above approach
using System;
 
class GFG
{
 
    // function to calculate nth
    // term of the series
    static long nthTerm(long n)
    {
        // variable nth will store the
        // nth term of series
        long nth;
     
        // if n is even
        if (n % 2 == 0)
            nth = 2 * ((n * n) - n);
     
        // if n is odd
        else
            nth = (2 * n * n) - n;
     
        // return nth term
        return nth;
    }
     
    // Driver code
    public static void Main()
    {
        long n;
        n = 5;
        Console.WriteLine(nthTerm(n));
     
        n = 25;
        Console.WriteLine(nthTerm(n));
     
        n = 25000000;
        Console.WriteLine(nthTerm(n));
     
        n = 250000007;
        Console.WriteLine(nthTerm(n));
    }
}
 
// This code is contributed by chandan_jnu

PHP




<?php
// function to calculate nth term
// of the series
function nthTerm($n)
{
    // variable nth will store the
    // nth term of series
    $nth;
 
    // if n is even
    if ($n % 2 == 0)
        $nth = 2 * (($n * $n) - $n);
 
    // if n is odd
    else
        $nth = (2 * $n * $n) - $n;
 
    // return nth term
    return $nth;
}
 
// Driver code
$n = 5;
echo nthTerm($n), "\n";
 
$n = 25;
echo nthTerm($n), "\n";
 
$n = 25000000;
echo nthTerm($n), "\n";
 
$n = 250000007;
echo nthTerm($n), "\n";
 
// This code is contributed by jit_t
?>

Javascript




<script>
 
// function to calculate nth term of the series
function nthTerm( n)
{
    // variable nth will store the nth term of series
   let nth;
 
    // if n is even
    if (n % 2 == 0)
        nth = 2 * ((n * n) - n);
 
    // if n is odd
    else
        nth = (2 * n * n) - n;
 
    // return nth term
    return nth;
}
 
// Driver code
 
 
    let n = 5;
 
    document.write( nthTerm(n) + "<br/>");
 
    n = 25;
   document.write( nthTerm(n) + "<br/>");
 
    n = 25000000;
    document.write( nthTerm(n) + "<br/>");
 
    n = 250000007;
    document.write( nthTerm(n) + "<br/>");
     
 
// This code contributed by gauravrajput1
 
</script>
Output: 
45
1225
1249999950000000
125000006750000091

 

Attention reader! Don’t stop learning now. Get hold of all the important mathematical concepts for competitive programming with the Essential Maths for CP Course at a student-friendly price. To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.




My Personal Notes arrow_drop_up
Recommended Articles
Page :