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

Terms

a(0) =122a(1) =272a(2) =482a(3) =666a(4) =1202a(5) =2092a(6) =3308a(7) =5398a(8) =8876a(9) =14232a(10) =22734a(11) =36346a(12) =57712a(13) =91204a(14) =143828a(15) =226126a(16) =354436a(17) =554296a(18) =865004a(19) =1347042a(20) =2093774a(21) =3248860a(22) =5032926a(23) =7784734a(24) =12023856a(25) =18546144