#include <stdio.h>
//a{n} = -6a{n-1} -9a{n-2}, a{1}=1, a{2}=2(再帰あり版)
int c=0;    //グローバル変数cの宣言
int rec(int n){
	c++;   //呼び出した階数のカウント
	if(n == 1){
		return 1;
	}
	else if(n == 2){
		return 2;
	}
	else{
		return -6*rec(n-1)-9*rec(n-2);
	}
}
 
int main(void) {
    int n = 5;
    printf("数列a%dの値は%d\n", n, rec(n));
    printf("rec関数の呼び出し回数は%d回です",c);
	return 0;
}
 
 

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