a(n) = A024733(n+3)/7.

Terms

a(0) =1a(1) =1a(2) =1a(3) =8a(4) =15a(5) =22a(6) =78a(7) =190a(8) =400a(9) =1051a(10) =2535a(11) =6721a(12) =16640a(13) =41553a(14) =106597a(15) =275234a(16) =701268a(17) =1767487a(18) =4523226a(19) =12032511a(20) =31091390a(21) =79566390a(22) =206917572a(23) =552688025a(24) =1439957527a(25) =3731510679a(26) =9775071839a(27) =26240674825a(28) =68869388526a(29) =179940240495