求给定数列的第 n 项
假设数列的前两个项为 1 和 6 ，数列的所有元素都比前后数的平均值少 2。任务是打印该系列的第 n 个个术语。 该系列的前几个术语是:
1, 6, 15, 28, 45, 66, 91, …
例:
输入: N = 3 输出: 15 输入: N = 1 输出: 1
方法:给定的数列表示三角形数列中的奇数。由于 n 第 个三角数很容易被 (n * (n + 1) / 2) 找到，所以为了找到奇数，我们可以将 n 替换为(2 * n)–1作为(2 * n)–1将总是产生奇数，即给定系列的 n 第 个数字将是【T25】 以下是上述方法的实施:
C++
// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
// Function to return the nth term
// of the given series
int oddTriangularNumber(int N)
{
return (N * ((2 * N) - 1));
}
// Driver code
int main()
{
int N = 3;
cout << oddTriangularNumber(N);
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java implementation of the approach
class GFG
{
// Function to return the nth term
// of the given series
static int oddTriangularNumber(int N)
{
return (N * ((2 * N) - 1));
}
// Driver code
public static void main(String[] args)
{
int N = 3;
System.out.println(oddTriangularNumber(N));
}
}
// This code contributed by Rajput-Ji
Python 3
# Python 3 implementation of the approach
# Function to return the nth term
# of the given series
def oddTriangularNumber(N):
return (N * ((2 * N) - 1))
# Driver code
if __name__ == '__main__':
N = 3
print(oddTriangularNumber(N))
# This code is contributed by
# Surendra_Gangwar
C
// C# implementation of the approach
using System;
class GFG
{
// Function to return the nth term
// of the given series
static int oddTriangularNumber(int N)
{
return (N * ((2 * N) - 1));
}
// Driver code
public static void Main(String[] args)
{
int N = 3;
Console.WriteLine(oddTriangularNumber(N));
}
}
/* This code contributed by PrinciRaj1992 */
服务器端编程语言（Professional Hypertext Preprocessor 的缩写）
<?php
// PHP implementation of the approach
// Function to return the nth term
// of the given series
function oddTriangularNumber($N)
{
return ($N * ((2 * $N) - 1));
}
// Driver code
$N = 3;
echo oddTriangularNumber($N);
// This code is contributed by Ryuga
?>
java 描述语言
<script>
// Javascript implementation of the approach
// Function to return the nth term
// of the given series
function oddTriangularNumber(N)
{
return (N * ((2 * N) - 1));
}
// Driver code
let N = 3;
document.write(oddTriangularNumber(N));
// This code is contributed by subham348.
</script>
Output:
15
版权属于：月萌API www.moonapi.com，转载请注明出处
