Number of n X 2 0..1 arrays with each 1 adjacent to 0, 2 or 4 king-move neighboring 1s.

Terms

a(0) =3a(1) =9a(2) =21a(3) =57a(4) =153a(5) =393a(6) =1041a(7) =2745a(8) =7185a(9) =18921a(10) =49761a(11) =130713a(12) =343761a(13) =903753a(14) =2375553a(15) =6245625a(16) =16419249a(17) =43163817a(18) =113476065a(19) =298319193a(20) =784254225a(21) =2061749001a(22) =5420172609a(23) =14249195961a(24) =37460035185a(25) =98479462761a(26) =258894708897