二十面体数
给定一个数 n，求第 n 个二十面体数。二十面体数是一类表示二十面体(有 20 个面的多面体)的比喻数。 前几个二十面体数字是 1，12，48，124，255，456，742，1128，1629……..
示例:
Input : 5
Output :255
Input :10
Output :2260
二十面体数的第 n项由下式给出:
上述思想的基本实现:
C++
// Icosahedral number to find
// n-th term in C++
#include <bits/stdc++.h>
using namespace std;
// Function to find
// Icosahedral number
int icosahedralnum(int n)
{
// Formula to calculate nth
// Icosahedral number &
// return it into main function.
return (n * (5 * n * n - 5 * n + 2)) / 2;
}
// Driver Code
int main()
{
int n = 7;
cout << icosahedralnum(n);
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Icosahedral number to find
// n-th term in Java
import java.io.*;
class GFG {
// Function to find
// Icosahedral number
static int icosahedralnum(int n)
{
// Formula to calculate nth
// Icosahedral number &
// return it into main function.
return (n * (5 * n * n - 5 *
n + 2)) / 2;
}
// Driver Code
public static void main (String[] args)
{
int n = 7;
System.out.println(
icosahedralnum(n));
}
}
// This code is contributed by aj_36.
Python 3
# Python 3 Program to find
# nth Icosahedral number
# Icosahedral number
# number function
def icosahedralnum(n) :
# Formula to calculate nth
# Icosahedral number
# return it into main function.
return (n * (5 * n * n -
5 * n + 2)) // 2
# Driver Code
if __name__ == '__main__' :
n = 7
print(icosahedralnum(n))
# This code is contributed aj_36
C
// Icosahedral number to
// find n-th term in C#
using System;
class GFG
{
// Function to find
// Icosahedral number
static int icosahedralnum(int n)
{
// Formula to calculate
// nth Icosahedral number
// & return it into main
// function.
return (n * (5 * n * n -
5 * n + 2)) / 2;
}
// Driver Code
static public void Main ()
{
int n = 7;
Console.WriteLine(icosahedralnum(n));
}
}
// This code is contributed by ajit
服务器端编程语言（Professional Hypertext Preprocessor 的缩写）
<?php
// Icosahedral number to
// find n-th term in PHP
// Function to find
// Icosahedral number
function icosahedralnum($n)
{
// Formula to calculate nth
// Icosahedral number &
// return it into main function.
return ($n * (5 * $n * $n -
5 * $n + 2)) / 2;
}
// Driver Code
$n = 7;
echo icosahedralnum($n);
// This code is contributed by m_kit
?>
java 描述语言
<script>
// Icosahedral number to
// find n-th term in Javascript
// Function to find
// Icosahedral number
function icosahedralnum(n)
{
// Formula to calculate
// nth Icosahedral number
// & return it into main
// function.
return (n * (5 * n * n - 5 * n + 2)) / 2;
}
let n = 7;
document.write(icosahedralnum(n));
</script>
输出:
742
时间复杂度:O(1) T3】辅助空间: O(1)
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