what sequences most need extending?

[N. J. A. Sloane]

Dear Seqfans,  I got email asking me to propose
a sequence that a group of programmers could
work on as a challenge.  The following
constraints were suggested:



1) It must be NP-complete
2) It must be simple to describe
3) It should not have been widely explored
4) A solution must be easy to check (= it doesn't require a lot of 
computation)
5) It has to be computed from N=8 to at most 64


Does anyone have a good suggestion?

NJAS