[seqfan] Re: New seq A284172 from David Sycamore looks interesting

Vladimir Shevelev shevelev at bgu.ac.il
Fri Mar 24 16:23:28 CET 2017

A fine structure!

In motivation of that, I submitted a simpler 
sequence A284278. If to suppose that there 
are only finite primes p such that 2p-1 is also
primes, then, by your result, there is a place 
where A284172 would be generated by the
same  rule as A284278. 

 It is well known that the problem of the
infinity of such primes is unsolved up to now.

Best regards,

From: SeqFan [seqfan-bounces at list.seqfan.eu] on behalf of BenoƮt Jubin [benoit.jubin at gmail.com]
Sent: 23 March 2017 19:08
To: Sequence Fanatics Discussion list
Subject: [seqfan] Re: New seq A284172 from David Sycamore looks interesting

If I'm not mistaken, one has for n > 6,
a(2n+1) = 2n+3 if (n+2 is prime or n+1 is a P-prime), and 2 else,
a(2n)   = 3n+2 if n+1 is a P-prime, and n+2 else,
where I defined a P-prime as a prime p such that 2p-1 is prime (there
is probably a standard term for that property).


On Tue, Mar 21, 2017 at 9:59 PM, Neil Sloane <njasloane at gmail.com> wrote:
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