[RiverDood]

Your version makes sense only if everyone else's hole cards are gathered up after they are dealt out . . . "de-spaded" . . . cloned for people who want to keep playing their hands -- and then reshuffled into the deck for use in the flop, turn and river.

I try never to play in games where people do that.

It hurts my shot at the flush draw. It lets everyone else know exactly what I'm chasing. And it creates a spooky sense of deja vu that encourages cheating, palming, etc. In short, it's an ugly variant of poker -- and if that's what they play in your town, I'd move away.

In most of the rest of the U.S., we play where the hole cards are not available for the flop/turn/river, regardless of whether people fold them or play them. So in that case, there are only 32 cards left that can go into FTR.

If you want to stick with your assumptions about what's in the 18 hole cards that you don't see, then do the rest of your math with fewer cards left in the deck. (i.e. 6/32 * 5/31 . . . )

You'll end up with something very close to Sklansky's numbers. His are more accurate because you really don't know anything about other people's hole cards. There could be zero spades there or 10 spades there. They are just as unknown to you as the part of the deck that hasn't been dealt yet.