formulae using elementary functions for represent interger sequences

[Antonio Esposito]

Hallo to everybody on integer seqfan!
this is antonio esposito, from R&D computer department of italtel spa of
Italy, recently entered in this fan club.
After i have had a look to the OEIS, i noted,  for a lot of sequences
(too many in my opinion), the lack of an esplicit closed formula with
elementary operations in order to represent the integer sequence, often
a well known and important sequence.
Beyond, i know that there can be several different formulas for the same
sequence, some being simple and some complex,
and perhaps there maybe a matter of best, elegant or minimal formula, or
the like.
A doubt of mine is if such lack is deliberatly wanted, becouse such
formulas are of few or none interest, or there are other motivations in
doing so.    Can anybody of you to resolve me this doubt ? many thanks.

antonio esposito