a(n) = 1 + Sum_{k=0..n-5} binomial(n-4,k) * a(k).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =4a(7) =8a(8) =16a(9) =32a(10) =70a(11) =170a(12) =452a(13) =1277a(14) =3731a(15) =11145a(16) =34031a(17) =106888a(18) =348016a(19) =1180538a(20) =4173726a(21) =15320402a(22) =58053312a(23) =225891952a(24) =899492200a(25) =3660479037a(26) =15228099789a(27) =64831944993a(28) =282763031581