尼科彻斯定理

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            int m = scanner.nextInt();
            System.out.println(GetSequeOddNum(m));
        }
        scanner.close();
    }
    public static String GetSequeOddNum(int m) {
        int s = m / 2;
        int k = m * m;
        String str = "";
        if (m % 2 == 0) {
            str=String.valueOf(k-1)+"+"+String.valueOf(k+1);
            for (int i = 1; i < m / 2; i++) {
                str = String.valueOf(k - 2 * i - 1) + "+" + str + "+"
                        + String.valueOf(k + 2 * i + 1);
            }
        } else {
            str = String.valueOf(k);
            for (int i = 1; i <= m / 2; i++) {
                str = String.valueOf(k - 2 * i) + "+" + str + "+"
                        + String.valueOf(k + 2 * i);
            }
        }
        return str;
    }
}