a(n) is the number of binary strings of length n such that no subsequence of length 4 contains 3 or more ones.

A118647

a(n) is the number of binary strings of length n such that no subsequence of length 4 contains 3 or more ones.

Terms

    a(0) =2a(1) =4a(2) =7a(3) =11a(4) =19a(5) =33a(6) =57a(7) =97a(8) =166a(9) =285a(10) =489a(11) =838a(12) =1436a(13) =2462a(14) =4221a(15) =7236a(16) =12404a(17) =21264a(18) =36453a(19) =62491a(20) =107127a(21) =183646a(22) =314822a(23) =539695a(24) =925191a(25) =1586041a(26) =2718927a(27) =4661017a(28) =7990313a(29) =13697676

External references