[seqfan] Re: There are more terms in this sequence?
Jack Brennen
jfb at brennen.net
Thu Feb 3 21:07:27 CET 2011
I wouldn't include 0 myself, mainly because its list of positive
divisors is infinite, unlike every positive integer.
Note that 0 is not considered a pseudoperfect number,
according to the OEIS:
http://oeis.org/A005835
On 2/3/2011 11:16 AM, Andrew Weimholt wrote:
> I haven't the time to look for more terms, but I see no obvious reason to expect
> this sequence to be finite.
>
> As for the title, how about the following?
> Numbers equal to the sum of the squares of their first k divisors, for some k.
>
> You should also include a separate sequence for the k values:
> 1, 4, 11, 19, 31, ...(if I've counted correctly)
>
> Also, should we start with 0, since 0 is the sum of its first 0 divisors?
> I'm not sure - maybe other seqfans can weigh in on this question.
>
> Andrew
>
>
> On 2/3/11, Claudio Meller<claudiomeller at gmail.com> wrote:
>> There are more terms in this sequence?
>> Is good the title ?
>>
>> Numbers that are equal to the sum of the squares of his first divisors
>>
>> 1, 130, 1860, 148840, 3039520
>>
>> 130 (1, 2, 5, 10) 1^2+2^2+5^2+10^2 = 1+4+25+100 = 130
>>
>> 1860 (1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30)
>>
>> 148480 (1, 2, 4, 5, 8, 10, 16, 20, 29, 32, 40, 58, 64, 80, 116, 128, 145,
>> 160, 232)
>>
>> 3039520 (1, 2, 4, 5, 8, 10, 11, 16, 20, 22, 32, 40, 44, 55, 80, 88, 110
>> 121, 157, 160, 176, 220, 242, 314, 352, 440, 484, 605, 628, 785, 880) 121,
>> 157, 160, 176, 220, 242, 314, 352, 440, 484, 605, 628, 785, 880)
>>
>> Thanks,
>> Claudio
>>
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