#include <stdio.h>
//a{n+1} = -2a{n} + 4, a{0}=2(再帰なし版)
int main(void) {
    int n = 4;
    int an=2;
    for(int i=0;i<n;i++){
    	an=-2*an+4;
    }
    printf("数列a%dの値は%d\n", n
, an
);  
	return 0;
}
 
 
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