mersenneforum.org I think I have a conjecture
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 2019-04-16, 20:55 #1 MathDoggy   Mar 2019 5·11 Posts I think I have a conjecture I have been studying some kind of numbers, the numbers that I have analyzed are of the form k*2^n-3 that never yield composite numbers and where k is a positive odd integer and I conjectured that 121 is the smallest k that never yields a prime number of the form k*2^n-3 Why do I think this conjecture is true? Well, I have checked n for 121 up to 31 and have not found any prime number. Thank you for reading. If you have any counterexamples, critics (as always ������), or ideas leave them in the comments please Attached Thumbnails   Last fiddled with by Batalov on 2019-04-16 at 22:36 Reason: post is completely replaced by MathDiggy. Attached is the screenshot of the original post
 2019-04-16, 20:59 #2 Batalov     "Serge" Mar 2008 Phi(4,2^7658614+1)/2 100011110010012 Posts Ahem.... x^n-y^n=z^n also means (rearranging...) x^n=z^n+y^n Doesn't it remind us anything?
2019-04-16, 21:05   #3
MathDoggy

Mar 2019

5510 Posts

Quote:
 Originally Posted by Batalov Ahem.... x^n-y^n=z^n also means (rearranging...) x^n=z^n+y^n Doesn't it remind us anything?
Yes, Fermat’s Last Theorem

2019-04-16, 21:06   #4
MathDoggy

Mar 2019

5×11 Posts

Quote:
 Originally Posted by Batalov Ahem.... x^n-y^n=z^n also means (rearranging...) x^n=z^n+y^n Doesn't it remind us anything?
I did not know that you could rearrange the equation Iike that

2019-04-16, 21:11   #5
Batalov

"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

9,161 Posts

Quote:
 Originally Posted by MathDoggy I did not know that you could rearrange the equation Iike that
Let's see.
Suppose I have
7 - 3 = 4
You are not sure that you can add 3 to both sides and get the equation
7 = 4 + 3 ?

 2019-04-16, 21:18 #6 MathDoggy   Mar 2019 5×11 Posts The ????? sign is a laugh emoji
2019-04-16, 21:21   #7
MathDoggy

Mar 2019

678 Posts

Quote:
 Originally Posted by Batalov Let's see. Suppose I have 7 - 3 = 4 You are not sure that you can add 3 to both sides and get the equation 7 = 4 + 3 ?
Now you are laughing about me, great!

 2019-04-16, 21:23 #8 Batalov     "Serge" Mar 2008 Phi(4,2^7658614+1)/2 9,161 Posts I am not laughing - I don't even see your posts anymore. You are now on my "Ignore" list. Bye! Of note: the original post was replaced full length with some other noise (fiddled by MathDoggy on 2019-04-16 at 13:18 ). That's not what people usually do here. Here is the screenshot of the original posting. Attached Thumbnails
2019-04-16, 21:25   #9
MathDoggy

Mar 2019

5·11 Posts

Quote:
 Originally Posted by Batalov I am not laughing - I don't even see your posts anymore. You are now on my "Ignore" list. Bye!
That is good

2019-04-17, 02:33   #10
dcheuk

Jan 2019
Pittsburgh, PA

22·59 Posts

Quote:
 Originally Posted by MathDoggy I have been studying some kind of numbers, the numbers that I have analyzed are of the form k*2^n-3 that never yield composite numbers and where k is a positive odd integer and I conjectured that 121 is the smallest k that never yields a prime number of the form k*2^n-3 Why do I think this conjecture is true? Well, I have checked n for 121 up to 31 and have not found any prime number. Thank you for reading. If you have any counterexamples, critics (as always ������), or ideas leave them in the comments please
You should define your terms more clearly and honestly use better English - what you are saying is ambiguous if at all make sense. Also try to be nicer to people, retracting statements are just not cool.

Quote:
 ... of the form k*2^n-3 that never yield composite numbers and where k is a positive odd integer...
This statement makes no sense, if we let k=3 then $$3\cdot2^n-3=3(2^n-1)$$ which is always composite for each integer $$n\geq2$$. Now move on to the second part:

Quote:
 I conjectured that 121 is the smallest k that never yields a prime number of the form k*2^n-3
First of all, you do not need to say "never yields a prime number of the form k*2^n-3" because your equation is exactly "k*2^n-3." Simply stating that "... is never prime" suffices what you are claiming. Note that you used both "never yield composite numbers" and "never yield a prime number" in the same sentence. That is just sloppy.

Now, to show that 121 is the smallest k such that k*2^n-3 is not prime, you first need to show that each 1<=k<121, k*2^n-3 is not prime for every integer n>=0.

Anyway, your assumption that $$121\cdot2^n-3$$ cannot be a prime is false since $$121\cdot2^{9}-3=61949$$ is a prime number.

 2019-04-17, 04:10 #11 VBCurtis     "Curtis" Feb 2005 Riverside, CA 10001100010002 Posts It's one thing to post nonsense and learn from the replies you get; it's quite another to remove your entire post and replace it with something fully unrelated after being shown that you don't understand addition and subtraction. For me, that sort of hiding from your own ineptitude and misrepresenting what you said deserves a ban from even misc.math subforum.

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