Re: Program to output a subset of the composite numbers
On 15/08/18 21:25, tomusa...@gmail.com wrote: Yes, I will try it! Thank you kindly. Please provide some context when you reply. This is the fourth message that you've sent but there's no immediate clue to whom you are answering. TIA :-) -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence -- 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
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
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
tomusa...@gmail.com wrote: > 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 Like >>> def is_composite(n): ... return not is_prime(n) ... >>> print(list(islice((i for i in count(3, step=2) if is_composite(i) and is_composite((i+1)//2)), 20))) [15, 27, 35, 39, 49, 51, 55, 63, 65, 69, 75, 77, 87, 91, 95, 99, 111, 115, 119, 123] ? -- 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
Steven D'Aprano wrote: > On Wed, 15 Aug 2018 05:34:06 -0700, tomusatov wrote: > >> 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." > > > Do you have a function to test for primality? For now, I'll assume you do. > > > def is_prime(n): > # Returns True if n is prime, False otherwise. > # implementation left as an exercise > > > # 0 (and 1) are neither prime nor composite; skip them. > # 2 and 3 are prime; start at the first composite, 4 > i = 4 > for j in range(5, 1001): > if not is_prime(j): > print(i) > i = j I think that are "any numbers that are one less than a composite number" while the OP wants only composite numbers that are one less than a composite number". In code from itertools import count, islice def cntaoltacn(): prev = None for i in count(2): if is_prime(i): prev = None else: if prev is not None: yield prev prev = i print(list(islice(cntaoltacn(), 20))) # [8, 9, 14, 15, 20, 21, 24, 25, 26, 27, 32, 33, 34, 35, 38, 39, 44, 45, 48, 49] > > > The above will stop at 999. To go forever, use this instead: > > > > from itertools import count > i = 4 > for j in count(5): > if not is_prime(j): > print(i) > i = j > > > > Alternatively, if you have a function which efficiently returns primes > one at a time, you can do this: > > > n = 4 # start at the first composite > for p in primes(5): # primes starting at 5 > print(list(range(n, p-1)) > n = p + 1 > > > > This ought to print out lists of composites, starting with: > > [] > [] > [8, 9] > [] > [14, 15] > > > etc. Take care though: I have not tested this code. > > > -- https://mail.python.org/mailman/listinfo/python-list
Re: Program to output a subset of the composite numbers
On Wed, 15 Aug 2018 05:34:06 -0700, tomusatov wrote: > 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." Do you have a function to test for primality? For now, I'll assume you do. def is_prime(n): # Returns True if n is prime, False otherwise. # implementation left as an exercise # 0 (and 1) are neither prime nor composite; skip them. # 2 and 3 are prime; start at the first composite, 4 i = 4 for j in range(5, 1001): if not is_prime(j): print(i) i = j The above will stop at 999. To go forever, use this instead: from itertools import count i = 4 for j in count(5): if not is_prime(j): print(i) i = j Alternatively, if you have a function which efficiently returns primes one at a time, you can do this: n = 4 # start at the first composite for p in primes(5): # primes starting at 5 print(list(range(n, p-1)) n = p + 1 This ought to print out lists of composites, starting with: [] [] [8, 9] [] [14, 15] etc. Take care though: I have not tested this code. -- Steven D'Aprano "Ever since I learned about confirmation bias, I've been seeing it everywhere." -- Jon Ronson -- https://mail.python.org/mailman/listinfo/python-list
Re: Program to output a subset of the composite numbers
On Wed, Aug 15, 2018 at 8:36 AM wrote: > > 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 Since composite numbers are all the positive integers that are not prime and not one, I believe you can find code to produce a sequence of prime numbers, and you can subtract that sequence from the sequence of positive integers -- Joel Goldstick http://joelgoldstick.com/blog http://cc-baseballstats.info/stats/birthdays -- https://mail.python.org/mailman/listinfo/python-list
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
