#include <iostream>
using namespace std;

int mod = 1000000007;
int n, K;
int dp[300][50000];

int main() {
	int i, j;
	
	cin >> n >> K;
	
	dp[0][0] = 1;
	for (i = 0; i < n - 1; i++) {
		for (j = 0; j <= i * (i + 1) / 2; j++) {
			dp[i + 1][j] += dp[i][j];
			if (dp[i + 1][j] >= mod) dp[i + 1][j] -= mod;
			dp[i + 1][j + i + 2] += mod - dp[i][j];
			if (dp[i + 1][j] >= mod) dp[i + 1][j] -= mod;
		}
		for (j = 1; j <= (i + 1) * (i + 2) / 2; j++) {
			dp[i + 1][j] += dp[i + 1][j - 1];
			if (dp[i + 1][j] >= mod) dp[i + 1][j] -= mod;
		}
	}
	
	int ans = 0;
	for (j = 0; j <= K; j++) {
		ans += dp[n - 1][j];
		if (ans >= mod) ans -= mod;
	}
	cout << ans << endl;
	return 0;
}