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Table of primes

asked 2013-03-23 16:44:58 +0200

Luiz Roberto Meier gravatar image

Hello,

I'm trying to create a table (or matrix, what comes first) with the first rank is the primes_range from 2 to 29 and the first column with primes_range from 2 to 29 too.

Then, I want to add i[0] + j[0] = element 4 using the values above.

The reason for that is that I want to create a table of even elements based on Goldbach conjecture that says that an even is the sum of two equal (or different) primes:

4 = 2 + 2 6 = 3 + 3 8 = 3 + 5

The problem is that an even number can be written in several ways, example:

24 = 5 + 19 24 = 7 + 17 24 = 11 + 13 and so on..

The number 200 = 3 + 197 . So, my problem is to 'remember' in a for/loop the number 3. When I'm close to the even 200 the number variable that holds the first prime is far away from 3.

So, I think the solution maybe can be a combination or a value table or a matrix.

Thank you in advance.

P.S.: This is not a homework.

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What is the question?

fidbc gravatar imagefidbc ( 2013-03-23 18:11:32 +0200 )edit

I want to create a matrix of prime elements starting, say, from 2 up to 197 OR a matrix of elements starting from 2 up to 200 where the elements that are primes have another shape or color. If you don't understand I can DRAW it to you. Thank you.

Luiz Roberto Meier gravatar imageLuiz Roberto Meier ( 2013-03-25 09:03:52 +0200 )edit

It is more or less clear what you want to achieve. You just didn't state an explicit question. Is it about how to create a [matrix](http://www.sagemath.org/doc/reference/matrices/sage/matrix/constructor.html)? Is it about how to generate lists of [prime](http://combinat.sagemath.org/doc/reference/misc/sage/rings/arith.html#sage.rings.arith.primes) numbers? What do you mean by shape or color? I'm starting to think a python dict might suit your purposes better.

fidbc gravatar imagefidbc ( 2013-03-25 10:04:49 +0200 )edit

You can think about it as a group too. But, forget. I can learn it alone without your funny help.

Luiz Roberto Meier gravatar imageLuiz Roberto Meier ( 2013-03-27 00:09:09 +0200 )edit

There is no place for insult here. Moreover with somebody who tries to help and knows Sage much better than you ! As fidelbc said before : there is no question in your post and your aim is unclear.

vdelecroix gravatar imagevdelecroix ( 2013-03-29 08:30:01 +0200 )edit

@LuizRobertoMeier: I deleted your insulting comment. When everyone else except you is finding you unclear, you might want to consider the possibility that it's not that everyone except you is an idiot, it's that you've been more ambiguous than you think.

DSM gravatar imageDSM ( 2013-03-29 09:43:14 +0200 )edit

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answered 2013-03-29 08:33:48 +0200

vdelecroix gravatar image

I am not sure what is your aim, but the function prime_range returns you a list of the prime integers below a given bound

sage: prime_range(20)
[2, 3, 5, 7, 11, 13, 17, 19]
sage: prime_range(50)
[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47]
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Asked: 2013-03-23 16:44:58 +0200

Seen: 1,434 times

Last updated: Mar 29 '13