The sold-out crowd at the Herbst Theatre Sunday night got quite a lesson in mathematics. They learned that math (a) is a laugh riot and (b) has surprisingly little to do with numbers.

At least that was the case in the hands of Steve Martin, and, unexpectedly, the poster boy for chaos theory himself, Robin Williams.

Martin took the stage at the request of the Mathematical Sciences Research Institute, a Berkeley-based think tank for the numerically minded, for a City Arts & Lectures program titled "Funny Numbers." The idea was for Martin and MSRI special projects director Robert Osserman to converse onstage about things math-related.

It started out that way. Sort of.

"I have no idea why I'm here. I think it's because ZsaZsa wasn't available," Martin said.

But Osserman gently reminded him it's because math- and science-themed topics appear frequently in his prolific writings. (In fact, it was a discussion of "magic boxes" -- the mathematical equivalent of crossword puzzles, which figure prominently in Martin's soon-to-be-published new novel -- at a cocktail party that led to Sunday's Martin-Osserman matchup.)

Osserman started the discussion by producing an historical French volume of numbers games and then asked Martin to read from his piece "Hillbilly Scientists Postulate a Three-Dimensional Universe."

"And I thought this was going to be dull," Martin dead-panned.

Dull it was not. Martin had the middle-age-skewing crowd fighting for air with each quip, even as Osserman steered the conversation mathward. He even offered a musical interlude, pulling out his banjo for a couple songs.

"We figured out the banjo was mathematical," Martin said, prompting Osserman to explain how the frets on two banjos could be used for calculations in the absence of a slide rule. "And that would be so much more convenient," Martin added.

If the house was pleased with Martin's multifaceted performance, however, it swelled with giddiness when the comedian invited his friend Williams to join them onstage.

Outfitted with a microphone, a bottle of water and a stool, Williams made himself at home and launched into a series of stream-of-consciousness riffs on everything from math to politics to "Rain Man."

"You know, we can go now," Martin said to Osserman during a rare moment's pause in Williams' routine.

Martin didn't cede the spotlight, though. He held his own against livewire Williams and even helped rein him in when the comedy began to stray off course. Osserman, on the other hand, wisely sat back and let the comics run wild -- literally, with Martin strewing papers across the stage and Williams tossing apples ("The mathematicians are trashing the room!").

Osserman took passive control of the proceedings, briefly, by having them read passages from Martin's play "Picasso at the Lapin Agile" -- Williams as Albert Einstein and Martin as Ernest Hemingway and the bartender -- which at least kept Williams to a script (though he experimented with vocal stylings ranging from Marlon Brando to Elmer Fudd before settling on a German-Yiddish blend).

The evening's celebrity cameos didn't end with Williams. The audience also got a peek at a celebrated forelimb when Martin turned the spotlight -- or, rather, raised the house lights -- on the hand model who scribbled formulas on the big screen in "A Beautiful Mind." It was about as deep a mathematical connection as was established all night.

Not that anyone was complaining. Steve Martin, Robin Williams, banjo-picking, staged readings and ad-libbed routines from two masters -- that's a pretty impressive formula right there.

acrump@examiner.com