Number of n X 3 0..1 arrays with each 1 adjacent to 3 or 4 king-move neighboring 1's.

Terms

a(0) =1a(1) =3a(2) =6a(3) =9a(4) =26a(5) =74a(6) =163a(7) =535a(8) =1735a(9) =4960a(10) =15935a(11) =51598a(12) =159682a(13) =507871a(14) =1626269a(15) =5134567a(16) =16304686a(17) =51939793a(18) =164789906a(19) =523362014a(20) =1664172607a(21) =5285951875a(22) =16791701819a(23) =53363480620a(24) =169541243631a(25) =538639046154