[seqfan] Re: Nice nontrivial integer sequence

Tim Peters tim.peters at gmail.com
Sun Mar 12 02:58:01 CET 2023


The page for A360477

    https://oeis.org/A360447

contains

    FORMULA a(n) = a(n-1) + a(n+1) if a(n+1) < a(n)

I expect "a formula" to show a way to compute a(n), but that's not what
this is. It appears to be a claim about 3 consecutive terms in some cases,
but it's not a true claim. I think the first place it fails is at n=18:

 n  a(n)
17 59586
18 33733
19  7880

Then a(19) < a(18), but a(18) isn't anywhere near a(17) + a(19).

Alas, I can't think of a true claim related to what it says, so I can't
suggest "a fix". I don't believe anyone has "a formula" for a(n) in the
usual meaning of the word. Perhaps this section should just be deleted?


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