A mathematical error notwithstanding (only 44 men have been president since Grover Cleveland counts twice), Andrew Malcolm‘s column in the Sacramento Bee offers a fascinating look at one of the most unusual aspects of our new president.

When Donald Trump took the presidential oath Friday, he joined a select, well-known group of only 45 men who have been president of the United States during its 240-year history.

What’s less-known is that the billionaire also joined a little-known group, only the sixth member of a super-select group of men – those whose very first elected office was the U.S. presidency. (Not counting the first president, George Washington, a general who disdained political parties.)

Are there any patterns to these presidential oddities? Any instructive observations from their rise and their service in the White House?

Well, for starters, all six have been members of the Republican Party or its predecessor, the Whigs.

Half were retired generals, in effect, military chief executives. Two were wealthy businessmen, successful civilian executives. One was a career government executive who is the only person to ever head the executive and judicial branches of America’s government.

Only two of the six served two terms.

Americans have had an episodic but regular fascination with non-politicians as their elected national leader as a sort of refreshing political cleansing, a democratic reaffirmation that Everyman might rise to the country’s highest office, although few do. At other times, American voters have flirted with wealthy business candidates with no political experience – Republican Wendell Willkie in 1940 and Ross Perot in 1992. But neither came close.

In Trump’s case, clearly, his success is attributed in large part to his ability to tap into a widespread frustration and dissatisfaction with the way Washington has not worked and his Democratic opponent’s close connection to that closed, self-aggrandizing system, including incumbent President Barack Obama.