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Messages 20524 - 20553 of 21096   Oldest  |  < Older  |  Newer >  |  Newest
Messages: Simplify | Expand   (Group by Topic) Author Sort by Date ^
20524
I'm not sure I get only 5 factors. 2,3,5,11,821 . Note , I have also 821 ! No other found. Here my UBASIC program    10   P=1    20   P=nxtprm(P) ...
Norman Luhn
nluhn
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Jul 1, 2009
1:27 pm
20525
... I'm still working on the "why". I suspect it has something to do with how quickly iterates of eulerphi for a prime hit a power of 2. The phenomenon doesn't...
richard_in_reading
richard_in_r...
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Jul 1, 2009
1:44 pm
20526
... In line 50, use the modulus m3 = eulerphi(P-1). In line 40, use the modulus m4 = eulerphi(m3). In line 30, use the modulus m5 = eulerphi(m4). Below is a...
David Broadhurst
djbroadhurst
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Jul 1, 2009
4:22 pm
20527
... How to predict which sort of behaviour? For example the divisor 93408839 | 137^(137^(137^(137^(137^137)))) + 184 pops in and then out: ...
David Broadhurst
djbroadhurst
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Jul 1, 2009
5:50 pm
20528
... Let's use the shorthand notation (like you did) of "p^^n+k" to mean "p^p^..^p+k", where there are n p's. Using Jens's pari code, it's quite quick (c.20...
Mike Oakes
mikeoakes2
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Jul 1, 2009
6:15 pm
20529
Quick little prime chestnut for you: Find all primes of the form 4^n+n^4, where n is a positive integer....
Jack Brennen
jbrennen
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Jul 1, 2009
6:57 pm
20530
... Let f(n) = 4^n + n^4. If n is even, then so is f(n). If n is odd, then f(n) = (A(n) + B(n))*(A(n) - B(n)) with A(n) = 2^n + n^2 B(n) = 2^((n+1)/2)*n Hence...
David Broadhurst
djbroadhurst
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Jul 1, 2009
8:57 pm
20531
Hello all:   32(n!)**8+1 is composite for all n positive integer ??   Sincerely   Sebastian [Non-text portions of this message have been removed]...
Sebastian Martin Ruiz
s_m_ruiz
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Jul 2, 2009
12:02 am
20532
... For which n>1 is 4*n!^8 + 1 prime ?? Maximilian...
Maximilian Hasler
maximilian_h...
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Jul 2, 2009
12:23 am
20533
... I can shed some light on this behaviour. For any prime q, define b(q,n) by the recurrence relation b(q,n+1)=q^b(q,n), with initial condition b(q,0)=1. [So...
Mike Oakes
mikeoakes2
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Jul 2, 2009
12:29 am
20534
... There is no need to restrict this to q /prime/, it can be any integer. And the Theorem can be generalized to Theorem: For k any integer, if a prime p...
Mike Oakes
mikeoakes2
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Jul 2, 2009
12:58 am
20535
... Sebastian Martin Ruiz <s_m_ruiz@...> wrote:   ... On the contrary, the PNT makes it probable (but not yet provable) that there is an *infinite* number of...
David Broadhurst
djbroadhurst
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Jul 2, 2009
1:16 am
20536
correcting a typo, which does not seem to me to affect the argument: The probability that ((2*(n!))^8)/2+1 is prime is (heuristically) asymptotic to...
David Broadhurst
djbroadhurst
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Jul 2, 2009
1:23 am
20537
... Very nice! Can you give an example where the arithmetic progression is different from the so-far-observed case of "every powering after the first...
David Broadhurst
djbroadhurst
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Jul 2, 2009
1:33 am
20538
... For none. Proof: Set x = (n!)^2 in the identity 4*x^4 + 1 = (2*x^2 + 1)^2 - (2*x)^2 David (per proxy Léon François Antoine)...
David Broadhurst
djbroadhurst
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Jul 2, 2009
1:47 am
20539
... Err, Mike, how does the second line follow from the first? If x = y mod (p-1) then q^x = q^y mod p, in my book. Has one of us made a big boob? David...
David Broadhurst
djbroadhurst
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Jul 2, 2009
2:15 am
20540
... Right... of course! Bad example - that's not what I meant to say. Maybe, Is 8*n!^8+1 composite for all n>4 ? Probably not. Actually I don't mind at all....
Maximilian Hasler
maximilian_h...
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Jul 2, 2009
3:01 am
20541
... Indeed there is a nonsequitor, David :-( While I try and mend the proof (I still believe the Theorem to be true - HELP, anyone?), here are the results of a...
Mike Oakes
mikeoakes2
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Jul 2, 2009
7:26 am
20542
Here's a Lemma that should be both true and useful. For any non-zero integer q, define b(q,n) by the recurrence relation b(q,n+1)=q^b(q,n), with initial...
Mike Oakes
mikeoakes2
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Jul 2, 2009
10:07 am
20543
... For a prime p to occur twice with a gap in between then p must divide x^m^n+c and x+c but not x^n+c. It must therefore also divide the difference x^m^n-x...
richard_in_reading
richard_in_r...
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Jul 2, 2009
11:34 am
20544
... Not partucularly useful, I suggest. b(q.n) is a power of q. b(q,n+1) is a bigger power of q. So it is rather trivial that b(q,n)|b(q,n+1). Dressing that up...
David Broadhurst
djbroadhurst
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Jul 2, 2009
11:43 am
20545
... See my previous post of today for an unusual counterexample for q=3 Here's another for our favourite base, 137 137^^0+2136727 = 2 * 11 * 24281 ...
richard_in_reading
richard_in_r...
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Jul 2, 2009
1:01 pm
20546
... Isn't this equivalent to the not very interesting observation that x divides x^y when x and y are nonzero integers? If you were to define b(q,c,n) as...
richard_in_reading
richard_in_r...
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Jul 2, 2009
3:28 pm
20547
Maybe Sum Of Digits Is Prime - SODIP or SODIPS for more than one. So we have another name for "additive" primes in The Encyclopedia of Integer Sequences. An...
cino hilliard
hillcino368
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Jul 2, 2009
4:52 pm
20548
... No, it's not actually. If you set x=b(q,n), then b(q,n+1)=q^x, NOT x^y for some y, so your observation does not apply. But I do agree I didn't need an...
Mike Oakes
mikeoakes2
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Jul 2, 2009
5:25 pm
20549
... I did not find any such. The largest prime base for which I readily found such occurrences was q=41. For example: q=41;p=8876627;c=4824114; ...
David Broadhurst
djbroadhurst
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Jul 2, 2009
5:29 pm
20550
... Cool findings, thanks David and others. After some reflection, I could tell everyone why we shouldn't be surprised. It's from a very simple and more...
Mark Underwood
marku606
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Jul 2, 2009
5:53 pm
20551
... Here is a case with q=79: q=79;p=5591987;c=3385011; for(k=2,10,a=vector(k,j,q);print([lift(pmod(a,p)+c),a])) [4909930, [79, 79]] [0, [79, 79, 79]] [578606,...
David Broadhurst
djbroadhurst
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Jul 2, 2009
5:56 pm
20552
... The stakes have risen, Mark. You have to explain 3 features of the data that Richard Heylen has exposed: 1) some primes stay as divisors at successive...
David Broadhurst
djbroadhurst
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Jul 2, 2009
6:10 pm
20553
... Feature number one, where some primes stay forever as divisors, is a natural consequence. Specifically, if a factor appears twice in a row at two...
Mark Underwood
marku606
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Jul 2, 2009
6:38 pm
Messages 20524 - 20553 of 21096   Oldest  |  < Older  |  Newer >  |  Newest
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