题解 | #等差数列#
等差数列
https://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
import java.util.Scanner;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
// 等差数列公式 s_n=n*a1+n*(n-1)*d/2
int result = 2 * n + n * (n - 1) * 3 / 2;
System.out.print(result);
}
}
