Number of (n+1) X (1+1) 0..1 arrays with no 2 X 2 subblock having zero or two 1's.

Terms

a(0) =9a(1) =21a(2) =49a(3) =115a(4) =269a(5) =631a(6) =1477a(7) =3463a(8) =8109a(9) =19007a(10) =44517a(11) =104327a(12) =244381a(13) =572655a(14) =1341525a(15) =3143383a(16) =7364173a(17) =17254655a(18) =40424581a(19) =94714855a(20) =221903869a(21) =519914127a(22) =1218099893a(23) =2853948663a(24) =6686519981a(25) =15666114847a(26) =36704297445a(27) =85995716871