题解 | 牛牛学数列6

#include <stdio.h>

int sequence(int n) {
    if (n == 1) {
        return 0;
    } else if (n == 2 || n == 3) {
        return 1;
    } else {
        return sequence(n - 3) + 2 * sequence(n - 2) + sequence(n - 1);
    }
}

int main(void) {
    //输入一个整数
    int n = 0;
    scanf("%d", &n);

    int result = sequence(n);

    printf("%d\n", result);

    return 0;
}