Number of (n+2) X 9 0..2 matrices with each 3 X 3 subblock idempotent.

Terms

a(0) =1694a(1) =1221a(2) =1455a(3) =1657a(4) =2091a(5) =2656a(6) =3308a(7) =4272a(8) =5672a(9) =7588a(10) =10325a(11) =14312a(12) =20058a(13) =28377a(14) =40512a(15) =58215a(16) =84052a(17) =121832a(18) =177116a(19) =258031a(20) =376513a(21) =550059a(22) =804293a(23) =1176775a(24) =1722562a(25) =2522335a(26) =3694335a(27) =5411860a(28) =7928889a(29) =11617642