[seqfan] Re: Suggest to add first differences of A043555

[M. F. Hasler]

On Fri, Jul 12, 2024 at 12:10 AM brad klee via SeqFan <seqfan at list.seqfan.eu>
wrote:

> Most of the necessary details are now worked out here:
> https://community.wolfram.com/groups/-/m/t/3208738


What "necessary" details do you refer to?
There is PARI code for oeis.org/A043555 that allows anyone without any need
to pay or install anything
to compute instantly as many terms as they want of that sequence or its
first differences:
Just paste
[a(n)=my(d=digits(n, 3)); sum(i=2, #d, d[i]!=d[i-1])];
*for(n=last=1,10^4, print1(-last+last=a(n)", "))*

into https://pari.math.u-bordeaux.fr/gpwasm.html and you get 10^4 terms
immediately:
The computation takes less than 0.01 sec.)

It gives the sequence
0, 0, 1, -1, 1, 0, 0, -1, 1, 1, 0, -1, -1, 1, 1, 0, -1, 0, 1, 0, 0, -1, 1,
-1, 0, -1, 1, 1, 0, 1, -1, 1, 0, 0, -1, -1, 1, 0, -1, -1, 1, 1, 0, -1, 1,
1, 0, 0, -1, 1, -1, 0, -1, 0, 1, 0, 1, -1, 1, 0, 0, -1, 0, 1, 0, -1, -1, 1,
1, 0, -1, -1, 1, ...

Searching for such sequences was quite an issue in the past, since
originally, sequences started with the first element > 1,
and they were sorted according to that... (IDK whether that has been
improved...)

I have proposed these first differences as oeis.org/draft/A373470, we'll
see whether it is accepted.

- Maximilian