Katy Perry and John Mayer being together is still whipped-cream-shooting-from-your-boobs weird. But she did marry Russell Brand so ... it's probably a wash.

Regardless, Jaty or Kohn or whatever the tabloids are calling them are still on, and their latest relationship endeavor took them to Las Vegas. Because a place dubbed Sin City is exactly where you go when you want a little peaceful quality time together.

The two lovahs, who are more on-again/off-again than a light switch, headed to Vegas with a bunch of friends -- but relax, she didn't pull a Britney and visit the Little White Wedding Chapel. Instead, the posse opted for something much more romantic: a strip joint.

"They were together in a group," an onlooker told People. "As for whether they got dances, they were in a strip club ... you do the math."

In other words, when the couple and their entourage exited around 5 a.m., they left behind a shortage in dollar bills from which the US Mint will likely never recover.