s(n+3)/4, where s is A024739.

Terms

a(0) =1a(1) =2a(2) =4a(3) =10a(4) =24a(5) =56a(6) =132a(7) =344a(8) =880a(9) =2216a(10) =5568a(11) =14912a(12) =39248a(13) =101952a(14) =265216a(15) =718240a(16) =1925376a(17) =5115008a(18) =13574976a(19) =37150464a(20) =100744448a(21) =271103616a(22) =729513984a(23) =2008900096a(24) =5495163136a(25) =14942424576a(26) =40595259392a(27) =112428786176a(28) =309465434112a(29) =847395311616