#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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