a(n) = 1 + Sum_{k=1..n-4} a(k) * a(n-k-4).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =3a(7) =4a(8) =5a(9) =7a(10) =11a(11) =17a(12) =25a(13) =36a(14) =54a(15) =84a(16) =131a(17) =201a(18) =307a(19) =475a(20) =745a(21) =1172a(22) =1837a(23) =2878a(24) =4531a(25) =7173a(26) =11381a(27) =18057a(28) =28669a(29) =45624