[seqfan] (no subject)

Richard Mathar mathar at strw.leidenuniv.nl
Wed Mar 3 13:34:04 CET 2010

~s Re: A172043 and many more

ja> Date: Wed, 3 Mar 2010 09:30:43 +0100
ja> From: Joerg Arndt <arndt at jjj.de>
ja> To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
ja> Cc: vincenzo.librandi at tin.it
ja> Subject: [seqfan] Re: A172043 and many more
ja> Note that (n^2+1) factors into (2 and) primes
ja> of the form 4k+1 for all n
ja> The comment " See sequence of prime:(37, 83, 139, 281, 367,..."
ja> makes no sense at all.

This just means :The subsequence of primes in this sequence is 37, 83,
139... , I guess.

The exchange of the actual definition of the sequence with a description
on its properties is a common "feature" of these
submissions, perhaps an attempt to point out the "most important observation"
in the definition (in some fear that might be overlooked by the reader)
rather than to put that into a formula or comment. So if
one has doubts on Librandi submissions, it's frequently sufficient
to swap the formula and the definition, and (after careful checking
the math) then to move the definition into a comment like "most of the a(n)
... obey..." or "some of the terms of the sequence have the special
property .." etc.


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