[seqfan] Rif: A light variation
john.mason at lispa.it
john.mason at lispa.it
Wed Jan 20 14:16:36 CET 2016
Hi
with regard to "and is a permutation of the integers >0":
There will be, at some time in the integers > 0, a sequence of one hundred
composite numbers.
Some of these, in particular in the middle, will never give a resulting
prime when added to the last (single) digit of a(n-1). Therefore they will
not be in a(n).
Therefore a(n) is not a permutation of the integers > 0, and it would be
fun to find the first integer not present!
john
Da: Eric Angelini <Eric.Angelini at kntv.be>
Per: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
Data: 20/01/2016 10:57
Oggetto: [seqfan] A light variation
Inviato da: "SeqFan" <seqfan-bounces at list.seqfan.eu>
Hello SeqFans,
here is https://oeis.org/A055265 :
> a(n) is the smallest positive integer not already in the sequence
> such that a(n)+a(n-1) is prime, starting with a(1)=1.
I propose this variant:
E> a(n) is the smallest positive integer not already in the sequence
E> such that a(n)+[the last digit of a(n-1)] is prime, starting with
a(1)=1.
I guess E starts like this (and is a permutation of the integers >0):
E = 1,2,3,4,7,6,5,8,9,10,11,12,15,14,13,16,17,22,21,18,23,20,...
Best,
É.
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