Primefree sequences in the OEIS. A bad idea.

[Thomas Baruchel]

On Dim, oct 30, 2005 at 02:02:32 +0200, Alexandre Wajnberg wrote:
> This is a reason (among others) for accepting sequences not exclusively
> "pure maths".

I can understand your point of view ; I perfectly know that mine is
ONE point of view and not the single one, but a thing I find great
with OEIS is automatical parsing through computer programs looking
for relationships between sequences ; I also need sometime to perform
my own lookup on a local database through "personal" algorithms more
concerned with what I am looking for than superseeker is.

One thing that makes me upset is when after two nights of computing
I realize that my algorithms have spent so much time on a sequence
that seemed to be interesting because one of the terms had a significant
GCD with the integer I was studying, which term appeared to be some
palindromic in base 42 or whatever. Thinking that my program could
spend time by factoring 123456 and find a deep relation with my center
of interest and learn after that 123456 has the great mathematical
property of being... the number of a sequence containing numbers which
are themselves not numbers of sequences whose terms are... would make
me more upset.

Of course I know that what makes me upset can have some interest for
other people. Thus I built my own version of the database by downloading
all *.txt files and discarding all sequences whose description does
not contain the strings Ramanujan, Euler, Fibonacci, Lucas, etc.
Thus I have 2,500 sequences in my small database. It is a pity because
there are certainly many sequences that would also have some
interest to me, but I HAD to do it after so many wasted time on
prime numbers that are also prime when written from right to left
in base 10 or numbers meaning "hello world" when written in base 26.

Thus I agree with not putting too many sequences with no real
mathematical property in them. Anyway I am happy and will still take
in the OEIS what I need ;-)

-- 
Thomas Baruchel
  Home Page: http://baruchel.free.fr/~thomas/