[seqfan] Re: Another chemistry related sequence?

[Charles Greathouse]

I would be very happy to have sequences like these in the OEIS, if
only they were well-defined and not arbitrary.  Stable at "the normal
room temperature conditions" is ill-defined; half-life over 10^20
years is arbitrary.

Perhaps isotopes by stability, except that that's not defined on the
lower end unless/until all (or all but one) of 'stable' isotopes are
found to have finite half-lives.

Charles Greathouse
Analyst/Programmer
Case Western Reserve University

On Wed, Sep 2, 2009 at 8:24 PM, <franktaw at netscape.net> wrote:
> See http://en.wikipedia.org/wiki/Bismuth-209.  Bismuth 209 was long
> thought to be stable, but actually has a half-life of 1.9e19 years.  It
> is likely that other isotopes will be found to be slightly unstable;
> perhaps all are (proton decay is still a theoretical concept).
>
> Frankly, I think this whole area ought to be left out of the OEIS; but
> as long as A007656 is present, I suppose there's no reason to exclude
> it.
>
> Franklin T. Adams-Watters
>
> -----Original Message-----
> From: David Wilson <davidwwilson at comcast.net>
>
> a(43) = 0 as well.
>
> I think "stable" once meant "will never spontaneously decay." The
> poster boy
> for stability was the proton.
>
> Wikipedia states that protons are now thought to have minimum half-life
> of
> 10^36 years, yet are still called stable.
>
> I don't find a defined half-life cutoff point where unstable becomes
> stable,
> maybe it's a matter of application.
>
>
> ----- Original Message -----
> From: "Antti Karttunen" <antti.karttunen at gmail.com>
>
>> Here is an idea for atomic elements related sequence that should
>> be reasonably well defined:
>>
>> a(n) = The number of stable isotopes the element number n has.
>>
>> If the information in Wikipedia is correct, the sequence should start
> as:
>> 2,2,2,1,2,2,2,3,1,3,...
>>
>> Note that both a(83) ( http://en.wikipedia.org/wiki/Bismuth )
>> and a(92) ( http://en.wikipedia.org/wiki/Uranium ) should be 0.
>>
>>
>>
>> (Or is it? Okay, we can speculate about the eventual decaying of
> protons,
>> but... Also, I mean stable at "the normal room temperature
> conditions",
>> not
>> inside
>> a particle accelerator.)
>>
>>
>> Cheers,
>>
>> Antti.
>
>
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