[seqfan] Re: A046452

israel at math.ubc.ca israel at math.ubc.ca
Sun Jan 6 03:50:15 CET 2013


Shouldn't it specify that the prime factors are taken in increasing order? 
For example, 777= 7*3*37 is not in the sequence. Also perhaps state that 
the prime factors need not be distinct.

Robert Israel
University of British Columbia

On Jan 4 2013, Robert G. Wilson v wrote:

>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/
>>
>
>_______________________________________________
>
>Seqfan Mailing list - http://list.seqfan.eu/
>
>
>
>_______________________________________________
>
>Seqfan Mailing list - http://list.seqfan.eu/
>
>
>_______________________________________________
>
>Seqfan Mailing list - http://list.seqfan.eu/
>
>


More information about the SeqFan mailing list