[seqfan] Re: Two "dumb" sequences and a question

[Brendan McKay]

This is like the "all numbers are interesting" proof: If some numbers 
are not
interesting, then there is a smallest non-interesting number, which is 
clearly
an interesting property.

Regardless, I hope that neither sequence is added to OEIS. The value of OEIS
as a research tool is diluted every time useless made-up sequences are 
added.

Brendan.

On 30/11/2022 10:58 pm, Ali Sada via SeqFan wrote:
> Hi everyone,
>
> Please consider the two sequences below:
>
> 1) Sequence AX contains all OEIS sequences where the A number is a term in the sequence itself. For example, A000027 since 27 is a positive integer.
>
> 2) Sequence AY contains all OEIS sequences where either:
> a) the A number is not a term in the sequence (e.g., A000040, since 40 is not a prime number),
> or
> b) we don’t know if the A number is a term in the sequence or not (e.g., A329697).
>
> The question here is: Where should the number Y go? If we put it in sequence AY, then we know where it belongs and that contradicts the definition of AY.
> Also, it couldn’t be part of AX because Y is not a term of AY.
>
> I’m trying to have some basic understanding of set theory and I would really appreciate your feedback.
>
> Best,
>
> Ali
>
>
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