[seqfan] Re: A046452

Robert G. Wilson v rgwv at rgwv.com
Fri Jan 4 23:12:21 CET 2013


Harvey,

	I agree now that you are correct.

	Here is the Mmca: fQ[n_] := 
 Block[{t = Table[#[[1]], {#[[2]]}] & /@ FactorInteger[n]}, tt = Flatten@
IntegerDigits@ t; Length@ Flatten@ t == 3 && tt == Reverse@ tt];
Select[Range at 30000, fQ]

	And it produces:
{8, 27, 125, 343, 429, 507, 795, 1309, 1331, 1533, 1547, 1587, 2023, 2097,
3633, 3729, 3897, 5289, 5295, 5547, 6597, 7833, 8029, 8427, 9583, 9795,
12207, 12795, 13489, 13573, 14133, 14147, 14295, 15463, 15549, 15987, 16233,
17295, 20667, 22139, 28273, 28609, 28847, 28951, 29729, 29829}

Bob.

-----Original Message-----
From: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of Harvey P.
Dale
Sent: Friday, January 04, 2013 3:17 PM
To: Sequence Fanatics Discussion list
Subject: [seqfan] Re: A046452

Graeme:
	Then would this definition work: "Numbers n with three prime factors
such that the concatenation of those prime factors is a palindrome"?
	And why are the numbers I mentioned in my earlier email (below) not
in the current sequence?
	Best,
	Harvey
 

-----Original Message-----
From: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of Graeme
McRae
Sent: Friday, January 04, 2013 3:04 PM
To: Sequence Fanatics Discussion list
Subject: [seqfan] Re: A046452

Because the elements a(n) of sequence A046452 have nothing to do with n.
 It's just a list of numbers, a(n), satisfying the property.  I agree with
you, though, that the word "composite" is superfluous.

--Graeme McRae
Palmdale, CA


On Fri, Jan 4, 2013 at 11:58 AM, Harvey P. Dale <hpd at hpdale.org> wrote:

>             I believe I am misunderstanding something about the above 
> sequence.  Why aren't these numbers in the sequence: 3729, 28609, 
> 28847, 28951, 29729, 29829?  And why does the definition read, 
> "Concatenation of the 3 prime factors of composite a(n) is a 
> palindrome," rather than "Concatenation of the 3 prime factors of n is a
palindrome"?
>             Clarification would be appreciated.
>             Best,
>             Harvey
>
> _______________________________________________
>
> Seqfan Mailing list - http://list.seqfan.eu/
>

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