a(n) = 1 + Sum_{k=1..n-3} a(k) * a(n-k-3).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =3a(6) =4a(7) =6a(8) =10a(9) =16a(10) =25a(11) =41a(12) =69a(13) =115a(14) =192a(15) =326a(16) =558a(17) =955a(18) =1641a(19) =2839a(20) =4930a(21) =8578a(22) =14972a(23) =26222a(24) =46037a(25) =80988a(26) =142793a(27) =252307a(28) =446617a(29) =791885