Take the 2-minute tour ×
Arqade is a question and answer site for passionate videogamers on all platforms. It's 100% free, no registration required.

So, Xbox redeemable codes are 25 character case insensitive strings of letters and numbers. However, it has been suggested that not all letter/number combinations might appear (eg. 0/O). In the interest of fraud detection, what is the definitive (read as: {{Citation needed}}) list of possible characters which might make up this string?

Bonus points: given these additional rules, what are the number of possible strings that could be formed.

share|improve this question
    
While gaming related, I don't think this is a gaming question. Any 25-character string with the same restrictions will have the same possibilities. –  Matthew Read May 12 '11 at 15:48
    
@Matt the restrictions are sort of an aside (mostly to make the question more fun), it is the rules I am interested in. Gaming.SE has long been established as a source for questions about consoles and their services (cite). –  tzenes May 12 '11 at 15:50
2  
@Matt if you think this is a math question, please re-read it. –  tzenes May 12 '11 at 15:53
    
@tzenes The way you used "rules" and "restrictions" differently in your comment confused me. They're not different :P If the question's "What are the restrictions/rules for forming an Xbox code?" then yeah, not a math question. –  Matthew Read May 12 '11 at 15:58
1  
@Grace Note: Ah, nevermind—It's to resolve a debate in the comments here. –  SevenSidedDie May 12 '11 at 18:00
show 5 more comments

1 Answer

up vote 13 down vote accepted

I went straight to the source and just e-mailed Xbox Support. I didn't think they would answer, but to my surprise, they did respond (screenshot of email is the best proof i can give) with the invalid characters.

There are 8 invalid letters and 3 invalid digits:

A E I O U L S N      0 1 5

That leaves them with 18 valid letters and 7 valid digits:

B C D F G H J K M P Q R T V W X Y Z     2 3 4 6 7 8 9

With 25 characters needed for a code and 25 possible letters and digits, if my math is right, and it's entirely possible it is not, that's (18+7)25 which my calculator says is 8.8817842 × 1034, which equals a whole lot of different combinations.

Screenshot of the e-mail from Xbox Support: enter image description here

share|improve this answer
    
Shouldn't that be (18+7)^25? I don't have my math-brain on right now, but by analogy to binary-number size calculations: an 8-bit binary number gives 2^8 possible permutations, which is digits^length. In this case we have (18+7) available digits, and a length of 25: (18+7)^25 or 25^25… which, oh hey, in this specific case it doesn't matter which way around they are. ;) –  SevenSidedDie May 13 '11 at 16:47
    
@SevenSidedDie You are right, thanks for the heads up. –  Doozer Blake May 13 '11 at 17:41
    
Wonder why they don't use S or N. –  Raven Dreamer May 13 '11 at 18:31
    
@Raven Dreamer S is too much like the 5 they don't include. But I can't figure out why the N –  Doozer Blake May 13 '11 at 19:09
    
I would guess N because of M. B and 8 are both acceptable, and that surprises me a little. –  Dave DuPlantis May 13 '11 at 21:21
add comment

protected by Community Feb 5 at 23:00

Thank you for your interest in this question. Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.