Forbes publishes a list of the world’s billionaires once a year. Of the 380 self-made American billionaires who made the list over the past three years, 42 of them were born in September. Being a fall baby doesn’t guarantee that you’ll amass a great fortune,though. These men have dedicated their lives to hard work, and maybe they’ve had a few good ideas along the way as well.

Just look at the late Steve Jobs. He dropped out of college, just like 20% of the 292 self-made American billionaires like Bill Gates, Michael Dell, or Larry Ellison on Forbes most recent list, and some might venture to say Jobs did alright. While an asshole and can-do attitude can get you far, brain power is often a helping hand.

Mathematical prowess is one key that people use to unlock the door to billionaire land. Mathematical abilities are hereditary (thanks for being poor at math mom and dad), and most of the parents of American billionaires are engineers, accountants, or small business owners. Some of these mathematical genes were put to good use at Yale in the Skull and Bones club, a secret society of smart people. Members include Blackstone co-founder Steven Schwarzman and FedEx founder Frederick Smith.

While a job at Goldman Sachs may allow you to relish in the wonders of financial glory, a billionaire’s success seems highly dependent on the parents. Parents, start polishing those math skills you forgot in high school and try to conceive in January. Not only may your child benefit, but he or she will probably send some cash your way for instilling him/her with billionaire tools. Know more.