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Straight 2 Flush
Introduction
Straight 2 Flush is a blackjack side bet found on Dynasty electronic blackjack games. It pays based on the poker value of the player's first two cards and the dealer's up card.
Mathematically, the bet is the same thing as version 2 of 21+3.
I saw this bet at the Venetian Las Vegas on October 6, 2021.
Rules
Wins on the Straight 2 Flush bet are based on the poker value of the player's two initial cards and the dealer's up card. The bet pays 9 to 1 if the poker value of these three cards is a straight, flush, straight flush, or three of a kind. I presume a suited pair and singleton counts as a flush, for example suited 5-5-Q.
The following table shows my analysis for eight decks. It counts a suited three of a kind as a three of a kind. The lower right cell shows a house edge of 2.74%.
Eight Deck Analysis
| Event | Win | Combinations | Probability | Return |
|---|---|---|---|---|
| Straight flush | 9 | 24,576 | 0.002063 | 0.018568 |
| Flush | 9 | 700,928 | 0.058841 | 0.529572 |
| Straight | 9 | 368,640 | 0.030947 | 0.278519 |
| Three of a kind | 9 | 64,480 | 0.005413 | 0.048717 |
| All other | -1 | 10,753,536 | 0.902736 | -0.902736 |
| Total | 11,912,160 | 1.000000 | -0.027360 |
The next table summarizes the house edge for various numbers of decks.
House Edge
| Decks | House Edge |
|---|---|
| 1 | 13.30% |
| 2 | 7.26% |
| 4 | 4.24% |
| 6 | 3.24% |
| 8 | 2.74% |