FIBONACCI QUARTERLY, cilt.56, sa.1, ss.18-31, 2018 (ESCI)
A conditional recurrence sequence {q(n)} is one in which the recurrence satisfied by q(n) depends on the residue of n modulo some integer r >= 2. If a conditional sequence {q(n)} is a (strong) divisibility sequence then we define it as a conditional (strong) divisibility sequence. In this paper, we find some families of the conditional (strong) divisibility sequences for r = 2. These sequences are a generalization of the best known (strong) divisibility sequences in the literature, such as the Fibonacci sequence, the Lucas sequence, the Lehmer sequence, etc. Also, they contain some new fourth-order linear divisibility sequences which are different from the ones in the literature. An open problem is to determine the conditional (strong) divisibility sequences for r > 2.