Number of 3Xn 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 1 1 and 1 0 1 vertically.

Terms

a(0) =6a(1) =36a(2) =82a(3) =217a(4) =499a(5) =1014a(6) =2141a(7) =4188a(8) =8150a(9) =15670a(10) =29517a(11) =55523a(12) =103348a(13) =191593a(14) =353916a(15) =651316a(16) =1196664a(17) =2193747a(18) =4017137a(19) =7347906a(20) =13429145a(21) =24530862a(22) =44784850a(23) =81739060a(24) =149141623a(25) =272067741a(26) =496250336a(27) =905026713a(28) =1650411906