[seqfan] Re: Rif: A light variation

M. F. Hasler seqfan at hasler.fr
Wed Jan 20 14:41:36 CET 2016


It seems that 114 is the first integer not in this sequence.

Maximilian


On Wed, Jan 20, 2016 at 9:16 AM, <john.mason at lispa.it> wrote:

> 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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