a(n) = Sum_{k=0..floor(n/4)} binomial(2*n-7*k,k).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =4a(6) =6a(7) =8a(8) =11a(9) =18a(10) =29a(11) =44a(12) =64a(13) =96a(14) =148a(15) =228a(16) =345a(17) =519a(18) =786a(19) =1198a(20) =1824a(21) =2766a(22) =4190a(23) =6358a(24) =9661a(25) =14674a(26) =22268a(27) =33786a(28) =51284a(29) =77866