#include <stdio.h>
#define N 100
int seq(int n) {
	int s[N];
	int i;
	s[0] = 1;
	s[1] = 2;
	for(i = 2; i <= n; i++) {
		s[i] = 2 * s[i - 1] + s[i - 2];
	}
	return s[n];
}
int main() {
	int n = 4;
	printf("seq(%d)=%d", n, seq(n));
	return 0;
}