Number of (n+2) X 3 0..1 matrices with each 3 X 3 subblock idempotent.

Terms

a(0) =50a(1) =70a(2) =113a(3) =172a(4) =263a(5) =418a(6) =669a(7) =1064a(8) =1699a(9) =2734a(10) =4409a(11) =7108a(12) =11471a(13) =18538a(14) =29973a(15) =48464a(16) =78379a(17) =126790a(18) =205121a(19) =331852a(20) =536903a(21) =868690a(22) =1405533a(23) =2274152a(24) =3679603a(25) =5953678a(26) =9633209a(27) =15586804a(28) =25219919a(29) =40806634