Number of 3 X n 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 0 and 1 1 1 vertically.

Terms

a(0) =6a(1) =36a(2) =84a(3) =192a(4) =426a(5) =858a(6) =1704a(7) =3330a(8) =6390a(9) =12150a(10) =22938a(11) =43044a(12) =80424a(13) =149766a(14) =278160a(15) =515568a(16) =954072a(17) =1763304a(18) =3255666a(19) =6006342a(20) =11074116a(21) =20407650a(22) =37592934a(23) =69228330a(24) =127454070a(25) =234605316a(26) =431771328a(27) =794539482a(28) =1461954876a(29) =2689788048