Number of (n+2)X4 0..2 matrices with each 3X3 subblock idempotent.

Terms

a(0) =178a(1) =272a(2) =371a(3) =449a(4) =630a(5) =894a(6) =1221a(7) =1707a(8) =2440a(9) =3476a(10) =4979a(11) =7189a(12) =10414a(13) =15114a(14) =22001a(15) =32083a(16) =46840a(17) =68452a(18) =100119a(19) =146509a(20) =214482a(21) =314086a(22) =460049a(23) =673947a(24) =987416a(25) =1446808a(26) =2120063a(27) =3106745a(28) =4552782a(29) =6672030