[seqfan] Re: tau and sigma
Frank Adams-Watters
franktaw at netscape.net
Fri Jul 31 15:16:17 CEST 2015
Is the sequence of all numbers n with tau(n+1) = tau(n-1) and sigma(n-1) = sigma(n+1) in the database? Likewise for the second one? I'm not sure either of those should be accepted, but don't even consider adding a sequence "primes with property P" unless "numbers with property P" is already there, or at the very least is submitted at the same time.
(Of course, this doesn't apply if P is really only applicable to primes, e.g. if it involves primitive roots.)
Franklin T. Adams-Watters
-----Original Message-----
From: юрий герасимов <2stepan at rambler.ru>
To: seqfan <seqfan at list.seqfan.eu>
Sent: Fri, Jul 31, 2015 1:07 am
Subject: [seqfan] tau and sigma
Dear SeqFans,
919, 13333097, 13358407, 70779463, 105125921, 110495719,
292840063, 321860263, 415520359, 617684959, 628112717, 993590681,...
--> primes
p satisfyng tau(p + 1) = tau(p - 1) and sigma(p + 1) = sigma(p - 1);
53,
20543, 47843, 32003407, 59808803, 96144127, 113561243, 238818893, 1020720293,
...
--> primes p satisfyng tau(p + 2) = tau(p - 2) and sigma(p + 2) = sigma(p -
2).
1-th sequence or 2-th sequence is of general interest?
Thanks.
JSG.
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