Program to output a subset of the composite numbers
I am not terribly familiar with Python, but am currently authoring an integer sequence for www.oeis.org and was wondering if anyone in the community could help me with authoring a Python program that outputs, "Composite numbers that are one less than a composite number." Thanks! Musatov -- https://mail.python.org/mailman/listinfo/python-list
Re: Program to output a subset of the composite numbers
Thank you very much! Do you also know how I might slightly alter to composite numbers that are one less than twice a composite number? 15 would be the first number Since 8 is composite then 2*8=16 16 - 1=15 Is composite -- https://mail.python.org/mailman/listinfo/python-list
Re: Program to output a subset of the composite numbers
Thanks, I think that is an interesting tactic. From there what might the language look like to filter out the composites that are not one less than twice another composite number? -- https://mail.python.org/mailman/listinfo/python-list
Re: Program to output a subset of the composite numbers
DATA 15, 27, 35, 39, 49, 50, 51, 55, 63, 65, 69, 75, 77, 87, 91, 95, 99, 111, 115, 119, 123, 125, 129, 135, 143, 147, 153, 155, 159, 161, 169, 171, 175, 183, 185, 187, 189, 195, 203, 207, 209, 215, 219, 221 -- https://mail.python.org/mailman/listinfo/python-list
Re: Program to output a subset of the composite numbers
I'm sorry I did not correctly state the subset I was after: "Composite numbers that are one less than twice a composite." The output would begin: DATA 15, 27, 35, 39, 49, 50, 51, 55, 63, 65, 69, 75, 77, 87, 91, 95, 99, 111, 115, 119, 123, 125, 129, 135, 143, 147, 153, 155, 159, 161, 169, 171, 175, 183, 185, 187, 189, 195, 203, 207, 209, 215, 219, 221 -- https://mail.python.org/mailman/listinfo/python-list
Re: Program to output a subset of the composite numbers
Yes, I will try it! Thank you kindly. -- https://mail.python.org/mailman/listinfo/python-list
Generating a specific list of intsgers
I am looking for a program able to output a set of integers meeting the following requirement: a(n) is the minimum k > 0 such that n*2^k - 3 is prime, or 0 if no such k exists Could anyone get me started? (I am an amateur) Thanks, Musatov -- https://mail.python.org/mailman/listinfo/python-list
Re: Generating a specific list of intsgers
On Saturday, August 25, 2018 at 9:46:21 AM UTC-5, Richard Damon wrote: > On 8/25/18 10:27 AM, Dennis Lee Bieber wrote: > > On Sat, 25 Aug 2018 03:56:28 + (UTC), Steven D'Aprano > > declaimed the following: > > > >> On Fri, 24 Aug 2018 14:40:00 -0700, tomusatov wrote: > >> > >>> I am looking for a program able to output a set of integers meeting the > >>> following requirement: > >>> > >>> a(n) is the minimum k > 0 such that n*2^k - 3 is prime, or 0 if no such > >>> k exists > >>> > >>> Could anyone get me started? (I am an amateur) > >> > >> That's more a maths question than a programming question. Find out how to > >> tackle it mathematically, and then we can code it. > > I'd want more punctuation in that just to ensure I'm interpreting it > > properly -- I'm presuming it is meant to be parsed as: > > (n * (2 ^ k)) - 3 > > > > Suspect this needs to be attacked in the reverse direction -- generate > > a list of primes, add 3, determine if it is a multiple of powers of two. > > Though in that case, k = 1 would fit all since if it is a multiple 2^2 (4) > > it would also be a multiple of 2^1 (2), for all greater powers of 2.. > > > > prime 5 > > + 3 => 8 > > log_2 8 => 3<<< integral k > > 8 => 1 * (2 ^ 3) > > 2 * (2 ^ 2) > > 4 * (2 ^ 1) > > > > n=4, k=1 > > > > OTOH, if it is supposed to be (n*2) ^ k, or even worse (n*2) ^ (k-3) > > the solution becomes more difficult. > > > > > I think the issue is given n, find k. > > a(1): 1*2-3=-1 no, 1*4-3=1 no, 1*8-3 - 5 YES, a(1) = 3 > > a(2) 2*2-3 = 1, no 2*4-3=5 YES a(2) = 2 > > a(3) 3*2-3 - 3 YES, a(3) = 1 > > and so on. > > One path to solution is to just count up the k values and test each > result for being prime, except that will never return 0 to say no such k > exists. That will require some higher level of math to detect (or an > arbitrary cap on k, and we say we can say 0 if the only k is too big, > but with big nums, that would be VERY large and take a very long time. > > -- > Richard Damon Here is a sample output: 3, 2, 1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 2, 0, 1, 1, 0, 2, 1, 0, 1, 1, 0, 1, 2, 0, 1, 2, 0, 1, 1, 0, 3, 1, 0, 1, 1, 0, 2, 1, 0, 1, 2, 0, 1, 1, 0, 2, 1, 0, 1, 1, 0, 1, 1, 0, 1, 2, 0, 2, 1, 0, 3, 1, 0, 1, 2, 0, 1, 1, 0, 5, 2, 0, 1, 1, 0, 2, 1, 0, 3, 1, 0, 1 -- https://mail.python.org/mailman/listinfo/python-list
