I'm designing a card game that uses regular-ish playing cards and relatively simple rules.
Basically, the game comes down to comparing sets of cards (a "play", made up of 1-5 cards). Four players are dealt 16 cards each from a 160-card deck (the deck has 8 suits and 20 ranks, these being Spades, Swords, Cups, Hearts, Clubs, Wands, Coins, and Diamonds, and A, 2-15, Page, Jack, Bishop, Queen, and King), and then take turns paying a small ante and putting down a "play". This play must rank higher than the previous play or else the player must fold. The last player then wins the collected pot.
Now, for my test runs, I've used poker rules for hand ranks, but I wanted to base the final rules on real math. So, I want to see how likely each kind of hand is and rank them in that order.
However, I'm not entirely sure how to do this.
The basic question is: how can I quickly figure out how likely one is to get at least one pair when you draw 16 cards from the 160-card deck?
These are the valid plays I've come up with:
One High-card
One Pair
3-Card Flush (three cards of the same suit)
3-Card Straight (three cards in rank order)
3-Card Straight Flush
3-Count (three of a kind)
Two Pair (total of four cards)
4-Card Flush
4-Card Straight
4-Card Straight Flush
4-Count
Full House (three of a kind AND two of a kind)
5-card Flush
5-card Straight
5-card Straight Flush
Royal Straight in Spades (as in poker, highest possible rank, suit, and play)
It is noteworthy that when you put down a play, those cards leave your hand and cannot be used again but if, for instance, you play a high card, you only loose one card. Thus, the best strategy is usually to start with a low play and work your way up over several plays, so everyone has to ante several times, thus increasing the pot. You must balance saving high cards for the final play and responding to other player's actions.