#include <stdio.h>
//a{n}=2a_{n-1}+3, a{0}=-2(再帰無し版)
int main(void) {
int n,an;
n = 4;
an = -2;
for(int i=0;i<n;i++){
an = 2*an+3;
}
printf("数列anの%d番目の値は%d\n", n
, an
); return 0;
}
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