[seqfan] You wouldn't believe (fwd)

Richard Guy rkg at cpsc.ucalgary.ca
Sat Dec 20 18:45:24 CET 2008

Funsters & fansters might be amused by this
somewhat unlikely coincidence.  I had
calculated a couple of hundred terms of a
fourth order recurring sequence [it's
A005178 in OEIS, if you want details]
and was looking for the ranks of apparition
of various primes.  A 19-digit prime factor
of the 53rd term turned up as a substring
of the 103rd term!

Have a prime time in  7^2 x 41.    R.

---------- Forwarded message ----------
Date: Wed, 17 Dec 2008 09:24:06 -0700 (MST)
From: Richard Guy <rkg at cpsc.ucalgary.ca>
To: Hugh Cowie Williams <williams at math.ucalgary.ca>
Subject: You wouldn't believe

      before sending the final (??) version
of the quadric file, I decided I'd do a search
for larger primes just to see if there were
any double ranks.  While searching with


which is a factor of a(53), I discovered that it's
a substring of a(103):


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