# Thread: orster52: BJ indexes = Span21 indexes

1. ## orster52: BJ indexes = Span21 indexes

I play HiLo. For 6D,S17 bj and for 6D,H17,DDD Span21, I find the following plays have the same index number.
1010-6,1010-5,16-10R,15-10R,15-9R,A8-5,1010-4,A8-4,15-4,13-6,14-6,11-10,11-8,10-8,A7-3,A7-4,A9-6,A9-4,14-AR,16-8R. Now isn't that interesting for such different games to have 20 indexes in common? I created this list because I would stop when playing Span21 when I hit the same index, thinking, no no I'm making use of regular bj indexes. My brain now has learned to accept this.

2. ## Aruuba: Re: BJ indexes = Span21 indexes

> I play HiLo. For 6D,S17 bj and for 6D,H17,DDD Span21,
> I find the following plays have the same index number.
>
> 1010-6,1010-5,16-10R,15-10R,15-9R,A8-5,1010-4,A8-4,15-4,13-6,14-6,11-10,11-8,10-8,A7-3,A7-4,A9-6,A9-4,14-AR,16-8R.
> Now isn't that interesting for such different games to
> have 20 indexes in common? I created this list because
> I would stop when playing Span21 when I hit the same
> index, thinking, no no I'm making use of regular bj
> indexes. My brain now has learned to accept this.

They might be the same number but they are not the same relative to a neutral count.

I mean like a TC+6 in BJ might happen 10 times as often as a TC+6 in SP21.

Surrendering at -2 is a neg count in BJ but a positive one in SP21.

But anything that helps you remember what to do is all good. So thanks - I probably wouldn't have learned the split 10's index since it's so high but now I don't have to!

3. ## Katarina Walker: The reason why ...

With splitting tens, both ten and Ace give you a great hand. This is not the case with most other hands, apart from a hand total of 10, of course. At a count of +4, regardless of whether you are playing BJ or SP21, you have 9 high cards per deck (a very approximate model, of course). It's just that in Spanish 21, 1/4 of those high cards, on average, are Aces, and in BJ, 1/5.
In Spanish 21, the 25% Aces and unconditional win on 21 will give you are better chance of scoring high after you slit your tens, BUT, in BJ, the 80% tens will give you a higher chance of busting on that 5 or 6. So, it all evens out, so the indices are the same in both games. Cool, hey?

With indices in both games, since we are using the exact same counting system, the differences are because of two reasons: (1) the fact that tens constitute 80% of the high cards in BJ, but 75% in SP21, plus (2) the unconditional win on 21.
That's all. So you are going to get a WHOLE lot of indices the same if tens and Aces affect the hand the same way, e.g. both tens and Aces make the hand lose (as in 15 and 16, drawing either a ten or an Ace gives you a losing hand), or both tens and Aces make the hand win, as in the hand 10. That's why the stiff hand indices are quite similar in both games. Obviously, it helps if the same goes for the dealer.
It's a bit of an adjustment changing to SP21 from BJ. But the truth is that if you used BJ indices in SP21 together with SP21 basic strategy at neutral count, you would still be a hell of a lot better off than using no indices.
When I first started playing SP21, I used BJ indices from Wong's Professional Blackjack for a few years until I could generate my own, and I made heaps of money.
There is quite a bit of difference in the indices for hard 12, as only 1/4 of the cards bust it instead of 4/13 (plus the unconditional win on 21). As the stiff hand gets higher, the effect of the missing ten gets less and indices get closer to BJ.

5. ## zoomie: Re: Oops. I mean (5 x 4) + 4 = 24 high cards per deck at TC = +4, not 9!

I'm confused. With a single full deck there are only 16 (SP21) or 20 (BJ) high cards (up through Ace). What is the meaning of the calculation (5x4) + 4 ? BTW, thank you, Katarina, for your book and your continued explanatory posts.

6. ## What about Bob: Re: Oops. I mean (5 x 4) + 4 = 24 high cards per deck at TC = +4, not 9!

> I'm confused. With a single full deck there are only
> 16 (SP21) or 20 (BJ) high cards (up through Ace). What
> is the meaning of the calculation (5x4) + 4 ? BTW,
> explanatory posts.

(5 types of high cards (10,J,Q,K,A) * 4 suits) + TC of 4 =24

7. ## What about Bob: New Ooops

Of course i meant J,Q,K,A not 10,J,Q,K

8. ## Katarina Walker: Re: Oops. I mean (5 x 4) + 4 = 24 high cards per deck at TC = +4, not 9!

At TC = +4, there are 4 extra high cards per deck in Blackjack. Normally (at TC = 0) there are 5 x 4 = 20 high cards per deck, so at TC = +4, there will be 24 high cards per deck in Blackjack.
In Spanish 21, at TC = +4, there are 8 extra high cards per deck. Normally (at neutral Sp21 count of TC = -4), there are 4 x 4 = 16 high cards per deck, so at TC = +4, there will also be 24 high cards per deck.
The difference between the two games is that in BJ, 80% of these 24 high cards are ten-valued, the other 20% are Aces. In Spanish 21, 75% of these 24 high cards are ten-valued, and the other 25% of Aces. So even if the two games had the same rules, a TC of +4 in SP21 would be better than in BJ because of the extra Aces. Add in the liberal rules, and you an see why a TC of +4 is WAY better in SP21 than in BJ. Of course, since it's 8 above neutral in SP21 instead of 4 above neutral (as it is in BJ), it occurs with much lower frequency.
Note that referring to a TC of x as "x extra high cards per deck, on top of a base defined as 20 per deck" is only an approximate model. Obviously, we are talking about Hi-Lo as applied to both games.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•