Calculate the row sums of this triangle from the row index (starting at index 1) e.g.:

RowSumOddNumbers.java

package com.company;

class RowSumOddNumbers {
    public static int rowSumOddNumbers(int n) {
        return sum(lastElement(n)) - sum(lastElement(n - 1));
    }

    private static int lastElement(int n) {
        return ((n * n) + (n - 1));
    }

    private static int sum(int n) {
        int s = ((n + 1) / 2);
        return s * s;
    }
}

return Math.pow(n,3);