Number of n X n 0..7 matrices with each 2X2 subblock idempotent.

Terms

a(0) =8a(1) =32a(2) =200a(3) =318a(4) =700a(5) =1292a(6) =2476a(7) =4570a(8) =8406a(9) =15256a(10) =27498a(11) =49198a(12) =87530a(13) =154940a(14) =273084a(15) =479466a(16) =838944a(17) =1463400a(18) =2545472a(19) =4416198a(20) =7643450a(21) =13199732a(22) =22747870a(23) =39126778a(24) =67176430