Number of (n+2)X(n+2) 0..1 matrices with each 3X3 subblock idempotent.

Terms

a(0) =50a(1) =94a(2) =180a(3) =286a(4) =540a(5) =992a(6) =1668a(7) =2852a(8) =4870a(9) =8086a(10) =13318a(11) =21860a(12) =35536a(13) =57364a(14) =92210a(15) =147516a(16) =234942a(17) =372868a(18) =589854a(19) =930262a(20) =1463134a(21) =2295546a(22) =3593192a(23) =5612308a(24) =8748560a(25) =13611938a(26) =21141762a(27) =32782810