Number of (n+1) X 4 0..1 matrices with each 2 X 2 subblock idempotent.

Terms

a(0) =28a(1) =52a(2) =78a(3) =125a(4) =193a(5) =302a(6) =472a(7) =743a(8) =1175a(9) =1868a(10) =2982a(11) =4777a(12) =7673a(13) =12350a(14) =19908a(15) =32127a(16) =51887a(17) =83848a(18) =135550a(19) =219193a(20) =354517a(21) =573462a(22) =927708a(23) =1500875a(24) =2428263a(25) =3928792a(26) =6356682a(27) =10285073a(28) =16641325a(29) =26925938