#include <stdio.h>
 
static int count = 0;
 
// a[n] = -6a[n-1] - 9a[n-2], a[1] = 1, a[2] = 2 (再帰の例題版)
int rec(int n){
	count++;
    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の%dの値は%d\n", n, rec(n));
    printf("このときrecの呼び出し回数は%d",count);
    return 0;
}
 

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