#include <stdio.h>
//練習問題F
 
int func(int n){
    int a=-1;
     for (int i = 2; i <= n; i++) {
        a = 3 * a + 5;  // 漸化式の計算
    }
 return a;}
 
int main(void) {
	int n = 3;
 
    printf("数列anについて, n=%dのときの値は%d\n", n
, func
(n
)); 	return 0;
}
 
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