#include <stdio.h>
//練習問題G
int func(int n){
int a, b=2, c=1;
int i;
if(n == 1){
return c;
}
if(n == 2){
return b;
}
for(i = 3; i <= n; i++){
a = -2 * b + 2 * c;
c = b;
b = a;
}
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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