[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,
Vladimir
________________________________________
From: SeqFan [seqfan-bounces at list.seqfan.eu] on behalf of BenoĆ®t 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).
Benoit
On Tue, Mar 21, 2017 at 9:59 PM, Neil Sloane <njasloane at gmail.com> wrote:
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