[seqfan] Edit needed for dead link in A028491

[Gottfried Helms]

Concerning

https://oeis.org/A028491

  primes of the form M_p = (3^p-1)/2

---------------------------------------------

We have a reference/link to Paul Bourdelais

  Paul Bourdelais,
    <a href="http://listserv.nodak.edu/cgi-bin/wa.exe?A2=ind0906&L=nmbrthry&T=0&F=&S=&X=7769E632C9622BAE75&Y=paul.bourdelais%40gd-ais.com&P=999">
       A Generalized Repunit Conjecture</a>


but which does work no more.

Manually I could locate the artice with that address:

   https://listserv.nodak.edu/cgi-bin/wa.exe?A1=ind0906&L=NMBRTHRY

and one has then to select the correct article.
I feel unsafe to edit myself the entries of A028491 manually, please can someone
do this for me?

TIA, cordially -

Gottfried Helms