#include <stdio.h>
//練習問題E
int tri(int x){
	switch(x){
		case 0:
		return 0;
		break;
		case 1:
		return 0;
		break;
		case 2:
		return 1;
		break;
		default:
		return tri(x-1)+tri(x-2)+tri(x-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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