"Prime Rewards" Credit Card - Page 2

axn · 2011-01-20, 03:34

Why does this entire discussion remind me of this?

gd_barnes · 2011-01-20, 09:14

Can you tell us what kind of credit card it is? That is: Is it a MasterCard, Visa, Discover, etc.?

By using the link given, we can eliminate Diners Club and American Express since those only have 14 and 15 digits respectively but that only eliminates the ranges for the first 6 digits of 300xxx-305xxx, 34xxxx, and 36xxxx-38xxxx. But heh, every little bit helps. :-)

lavalamp · 2011-01-20, 19:21

From 0000 0002 to 9999 9941, there are 1,767,467 possibilities (out of 5,761,455 primes less than 10^8) for the last 8 digits. It only took pari/gp 15 seconds to count 'em up.

However continuing with the same naïve method I used would take another year, and you can add a bit more time on again for Luhn algorithm check.

Based on some flaky maths that wouldn't stand up to any scrutiny whatsoever, I'm going to guestimate there are about 800 billion combinations.

davar55 · 2011-01-20, 20:06

Quote:

Originally Posted by ixfd64

Man, I could see the headlines already...

"Mathematician becomes victim of fraud after posting credit card riddle online"

Followup:

CRIMINALS CAUGHT BY MERSENNE POLICE SQUAD.

Details follow.

davar55 · 2011-01-20, 20:08

Quote:

Originally Posted by axn

Why does this entire discussion remind me of this?

That's wrenchingly funny !

Hits the mark !

science_man_88 · 2011-01-20, 20:32

1) if we check for primes upto and including 9999 we get:

Code:

(16:22)>a=0;forprime(x=1,9999,a=a+1);print(a);
1229

2) without checking if they are prime we get 1229*10000 or 12290000 combos at the 8 digits level

3) continuing to 16 digits we come with 1229000000000000 combos as an absolute maximum.

science_man_88 · 2011-01-20, 21:32

Quote:

Originally Posted by science_man_88

1) if we check for primes upto and including 9999 we get:

Code:

(16:22)>a=0;forprime(x=1,9999,a=a+1);print(a);
1229

2) without checking if they are prime we get 1229*10000 or 12290000 combos at the 8 digits level

3) continuing to 16 digits we come with 1229000000000000 combos as an absolute maximum.

4) trying to go from 16 digits this popped up:

Code:

(17:29)>a=0;forstep(x=10000000000000001,9999999999999999,2,if(isprime(x) && isprime(x%100000000) && isprime(x%10000),a=a+1));print(a);
0

Doh! That's 17 digits no wonder.

ewmayer · 2011-01-20, 21:54

Science_man, of you can't be bothered to even read up on the most elementary aspects of number theory, just STFU, will you?

Good grief, that was some unbelievably stupid shit there. I had to delete it simply to keep this from turning into another 100-post flamefest between you and Bob Silverman.

science_man_88 · 2011-01-20, 22:02

Quote:

Originally Posted by ewmayer

Science_man, of you can't be bothered to even read up on the most elementary aspects of number theory, just STFU, will you?

Good grief, that was some unbelievably stupid shit there. I had to delete it simply to keep this from turning into another 100-post flamefest between you and Bob Silverman.

Why do you think i made the thread I'm trying to learn it from ? I do have a resource I found and I wasn't speculating I was doing calculation based on the number of prime numbers less than 10,000 or the prime numbers with 4 digits as part of the puzzle is based off how many 8 digit primes have a last four digits that form a prime. Up to you what you delete.

ewmayer · 2011-01-20, 22:13

Quote:

Originally Posted by science_man_88

Why do you think i made the thread I'm trying to learn it from ? I do have a resource I found

Your "resource" is to actually count the primes < 10000 (so far, so good, but a really dumb approach to the full-problem estimation), then multiply by 10000 to get an estimate of #primes < 10^8? I mean really...

"continuing to 16 digits we come with 1229000000000000 combos as an absolute maximum."

I don't know what kind of "resources" you are using, but even the first few paragraphs of the wikipedia entry for "prime number" alludes to the prime counting function.

Gah, why do I even bother...I just *had* to click "view post" instead of continuing to blissfully "ignore user".

science_man_88 · 2011-01-20, 22:26

Quote:

Originally Posted by ewmayer

Your "resource" is to actually count the primes < 10000 (so far, so good, but a really dumb approach to the full-problem estimation), then multiply by 10000 to get an estimate of #primes < 10^8? I mean really...

"continuing to 16 digits we come with 1229000000000000 combos as an absolute maximum."

I don't know what kind of "resources" you are using, but even the first few paragraphs of the wikipedia entry for "prime number" alludes to the prime counting function.

Gah, why do I even bother...I just *had* to click "view post" instead of continuing to blissfully "ignore user".

I was just saying as a maximum you can't have more than the number of 16 digit numbers that end in a 4 digit prime. maybe I should have said that instead of trying math?

2011-01-20, 09:14	#13
gd_barnes May 2007 Kansas; USA 3³·5·7·11 Posts	Can you tell us what kind of credit card it is? That is: Is it a MasterCard, Visa, Discover, etc.? By using the link given, we can eliminate Diners Club and American Express since those only have 14 and 15 digits respectively but that only eliminates the ranges for the first 6 digits of 300xxx-305xxx, 34xxxx, and 36xxxx-38xxxx. But heh, every little bit helps. :-) Last fiddled with by gd_barnes on 2011-01-20 at 09:18

2011-01-20, 20:32	#17
science_man_88 "Forget I exist" Jul 2009 Dumbassville 2⁶×131 Posts	1) if we check for primes upto and including 9999 we get: Code: (16:22)>a=0;forprime(x=1,9999,a=a+1);print(a); 1229 2) without checking if they are prime we get 1229*10000 or 12290000 combos at the 8 digits level 3) continuing to 16 digits we come with 1229000000000000 combos as an absolute maximum.

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2011-01-20, 03:34	#12
axn Jun 2003 1001110111100₂ Posts	Why does this entire discussion remind me of this?

2011-01-20, 19:21	#14
lavalamp Oct 2007 Manchester, UK 5×271 Posts	From 0000 0002 to 9999 9941, there are 1,767,467 possibilities (out of 5,761,455 primes less than 10^8) for the last 8 digits. It only took pari/gp 15 seconds to count 'em up. However continuing with the same naïve method I used would take another year, and you can add a bit more time on again for Luhn algorithm check. Based on some flaky maths that wouldn't stand up to any scrutiny whatsoever, I'm going to guestimate there are about 800 billion combinations.

2011-01-20, 21:54	#19
ewmayer ∂²ω=0 Sep 2002 República de California 103×113 Posts	Science_man, of you can't be bothered to even read up on the most elementary aspects of number theory, just STFU, will you? Good grief, that was some unbelievably stupid shit there. I had to delete it simply to keep this from turning into another 100-post flamefest between you and Bob Silverman.