#include <stdio.h>
//練習問題E
int tri(int n){
	if (n==0)
	return 0;
	else if (n==1)
	return 0;
	else if (n==2)
	return 1;
	else
	return tri(n-1)+tri(n-2)+tri(n-3);
}
 
 
 
int main(void) {
	int n = 7;
    printf("数列Tnについて, n=%dのときの値は%d\n", n
, tri
(n
)); 	return 0;
}
 
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