# [seqfan] Re: n = number of divisors of 2^n -1

Charles Greathouse charles.greathouse at case.edu
Wed Apr 28 22:57:01 CEST 2010

```I've finished looking for members of this sequence.  There are no more
up to 2^18 = 262 144.

Charles Greathouse
Analyst/Programmer
Case Western Reserve University

On Wed, Apr 21, 2010 at 4:01 PM, Charles Greathouse
<charles.greathouse at case.edu> wrote:
> Well, 32 is the last power of two in the sequence since
> (2^64-1)/(2^32-1) = 641 * 6700417 is composite.  Otherwise, I checked
> up to 16384 without finding any members.
>
> Charles Greathouse
> Analyst/Programmer
> Case Western Reserve University
>
> On Wed, Apr 21, 2010 at 2:00 PM, Leroy Quet <q1qq2qqq3qqqq at yahoo.com> wrote:
>> Oh, I see. You downloaded all of the numbers-of-divisors-of-(2^k-1)'s, and did not extend my sequence. Sorry for the confusion.
>>
>> Thanks,
>> Leroy Quet
>>
>> [ ( [ ([( [ ( ([[o0Oo0Ooo0Oo(0)oO0ooO0oO0o]]) ) ] )]) ] ) ]
>>
>>
>> --- On Wed, 4/21/10, Leroy Quet <q1qq2qqq3qqqq at yahoo.com> wrote:
>>
>>> From: Leroy Quet <q1qq2qqq3qqqq at yahoo.com>
>>> Subject: [seqfan] Re: n = number of divisors of 2^n -1
>>> To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
>>> Date: Wednesday, April 21, 2010, 5:51 PM
>>> I'm sorry. I don't know what you just
>>> did.
>>>
>>> The number of divisors of 2^12 -1 is 24, not 12. So, 12 is
>>> not in the list.
>>>
>>> Thanks,
>>> Leroy Quet
>>>
>>>
>>> [ ( [ ([( [ ( ([[o0Oo0Ooo0Oo(0)oO0ooO0oO0o]]) ) ] )]) ] )
>>> ]
>>>
>>>
>>> --- On Wed, 4/21/10, Richard Mathar <mathar at strw.leidenuniv.nl>
>>> wrote:
>>>
>>> > From: Richard Mathar <mathar at strw.leidenuniv.nl>
>>> > Subject: [seqfan] Re: n = number of divisors of 2^n
>>> -1
>>> > To: seqfan at seqfan.eu
>>> > Date: Wednesday, April 21, 2010, 5:34 PM
>>> >
>>> > lq> From: Leroy Quet <q1qq2qqq3qqqq at yahoo.com>
>>> > lq> To: seqfan at seqfan.eu
>>> > lq> Subject: [seqfan]  n = number of divisors of
>>> > 2^n -1
>>> > lq>
>>> > lq> I get the sequence where a positive integer n
>>> is
>>> > included if
>>> > lq> n = the number of divisors of 2^n - 1,
>>> > lq> begins:
>>> > lq> 1,2,4,6,8,16
>>> >
>>> >   sort -n -k 2 b046801.txt
>>> > which says that 12 is also in the list at n=21. Other
>>> > members in the list are
>>> >
>>> > 0 1 2 4 6 8 12 16 24 32 48 64 96 128 144 160 192 256
>>> 384
>>> > 512 768
>>> > 1024 1536 2048 3072 4096 4608 6144 8192 9216 10240
>>> 12288
>>> > 16384 24576
>>> > 32768 49152 65536 73728 98304 131072 147456 196608
>>> 262144
>>> > 294912
>>> > 393216 524288 655360 786432 etc
>>> >
>>> > but this is not necessarily a complete set, because
>>> the
>>> > bfile
>>> > is finite.
>>> >
>>> >
>>> > _______________________________________________
>>> >
>>> > Seqfan Mailing list - http://list.seqfan.eu/
>>> >
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>>
>>> Seqfan Mailing list - http://list.seqfan.eu/
>>>
>>
>>
>>
>>
>>
>> _______________________________________________
>>
>> Seqfan Mailing list - http://list.seqfan.eu/
>>
>

```