(Seem to be falling behind lately. If something I'm supposed to do then make sure it's under my nose!)
My various free software and mathematical write-ups at http://user42.tuxfamily.org/index.html
Email address there lightly obscured against spam, or unobscured on the seqfan list, or wiki email-this-user enabled here.
My bits of code most related to the OEIS include Perl grep for numbers in the stripped file (cf Hugo's FORTRAN), some Emacs bits, and Pari/GP recurrence guesser includes OEIS style "signature" and formula output.
The recurrence guesser includes an example program using Pari polmods for calculating terms in a recurrence. Polmod is a touch obscure, but is compact and efficient (faster and less memory than the more obvious matrix powering).