[seqfan] Re: Atomic number of n-th element in the "neptunium series"

[Neil Sloane]

If the sequence is just counting down by 4's from 149, it probably is not
worth adding to the OEIS

Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com


On Thu, Apr 19, 2018 at 7:52 AM, Allan Wechsler <acwacw at gmail.com> wrote:

> Every nucleus has an integer mass number; radioactive decay either doesn't
> change the mass number, or reduces it by 4. Therefore, there are four
> classes of radioactive nuclei. The Np-237 series all have mass number of
> the form 4n+1. It is called the Neptunium series because at the time of its
> discovery, Neptunium was the earliest known member. Four prior members are
> now known: Californium-249, Curium-245, Plutonium-241, and Americium-241
> (which decays into Neptunium-237).
>
> The 4n series's earliest known member is Californium-252 and is called the
> Thorium series; 4n+2 starts with Uranium-238 and is named after it; and
> 4n+3 starts with Californium-251 and is called the Actinium series.
>
> I have no opinion on whether the atomic numbers of these series belong in
> OEIS; they seem like a borderline case to me.
>
> On Thu, Apr 19, 2018 at 6:31 AM, Felix Fröhlich <felix.froe at gmail.com>
> wrote:
>
> > "Why Neptunium 237?"
> >
> > I chose it because it seems to have a long decay chain. There may be
> other
> > lements with longer chains, I am not sure. Also, I thought it was
> > interesting that the chain cannot have progressed past Bi-209 naturally
> due
> > to the extremely long half-life of Bi-209.
> >
> > Thanks for your suggestion regarding making each term the number of the
> > most common element. That sounds like a good idea.
> >
> > Regards
> > Felix
> >
> > 2018-04-19 1:55 GMT+02:00 Frank Adams-watters via SeqFan <
> > seqfan at list.seqfan.eu>:
> >
> > > If this is added, I think each term should be the atomic number of the
> > > most common element at that step.
> > > This "stabilizes " the sequence: otherwise at step n, if you discovered
> > > their was another decay product
> > > occurring only with, say, probability 0.001%, the sequence would have
> to
> > > be changed so that a(n) = 0.
> > >
> > > Second, why Neptunium 237? Is there something special about it?
> > >
> > > Franklin T. Adams-Watters
> > >
> > >
> > > -----Original Message-----
> > > From: Felix Fröhlich <felix.froe at gmail.com>
> > > To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
> > > Sent: Wed, Apr 18, 2018 7:41 am
> > > Subject: [seqfan] Atomic number of n-th element in the "neptunium
> series"
> > >
> > > Dear SeqFans,here is an idea for a sequence related to radioactive
> decay
> > > of a chemical
> > > element:
> > > Atomic number of n-th element in the "neptunium series", the decay
> chain
> > of
> > > neptunium-237, or 0 if the n-th link of the chain consists of more than
> > one
> > > element. For an overview, please see
> > > https://en.wikipedia.org/wiki/Decay_chain#Neptunium_series
> > > The sequence starts 93, 91, 92, 90, 88, 89, 87, 85, 83, 0, 82, 83,
> > 81a(10)
> > > (if the offset is 1) is 0, because bismuth-213 decays into
> > > polonium-213 and thallium-209, both of which in turn decay into
> lead-209.
> > > I don't know if this sequence is interesting. The "0" term may be a bit
> > > unsatisfactory, but I am not sure of a better way to resolve the issue
> of
> > > an
> > >  isotope decaying into two daughter isotopes at the moment.
> > >
> > > Best regardsFelix Fröhlich
> > >
> > > --Seqfan Mailing list - http://list.seqfan.eu/
> > >
> > > --
> > > Seqfan Mailing list - http://list.seqfan.eu/
> > >
> >
> > --
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> >
>
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