#include <stdio.h>
 
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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