#include <stdio.h>
//練習問題D
 
int func(int n) {
    if (n == 0) {
        return -1;  // a0 = -1
    } else {
        return 3 * func(n - 1) + 5;  // an = 3*a_{n-1} + 5
    }
}
 
int main(void) {
    int n = 3, m;
    m = func(n);
    printf("数列anについて, n=%dのときの値は%d\n", n
, m
);     return 0;
}
 
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