Mathalon_sum_A_sum_B

        int n = 10;
        int max_number = 9;
        int max_sum = max_number*n;
        BigInteger d[][] = new BigInteger[15][105];

        for(int i = 0;i<15;i++) for(int j = 0;j<105;j++)
            d[i][j] = BigInteger.ZERO;
        d[0][0] = BigInteger.ONE;
        for(int i = 0; i<n;i++)
        {
            for(int cur_sum = 0; cur_sum < max_sum; cur_sum++)
            {
                for(int j = 0; j<=max_number; j++)
                {
                   d[i+1][cur_sum + j] = d[i+1][cur_sum + j].add(d[i][cur_sum]);
                }
            }
        }

        BigInteger x = BigInteger.ZERO;
        for(int k = 0; k<=9*n;k++) {
            x = x.add(d[10][k].multiply(d[10][k]));
        }
        System.out.println(x);