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

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =2a(7) =4a(8) =8a(9) =16a(10) =32a(11) =66a(12) =148a(13) =374a(14) =1052a(15) =3156a(16) =9724a(17) =31096a(18) =104124a(19) =366696a(20) =1355624a(21) =5220120a(22) =20763160a(23) =84944720a(24) =357759200a(25) =1557192440a(26) =7029575320a(27) =32929457880a(28) =159764303320a(29) =800509163360