1/4 the number of (n+1) X 9 binary arrays with all 2 X 2 subblock sums the same.

Terms

a(0) =153a(1) =155a(2) =158a(3) =164a(4) =174a(5) =194a(6) =230a(7) =302a(8) =438a(9) =710a(10) =1238a(11) =2294a(12) =4374a(13) =8534a(14) =16790a(15) =33302a(16) =66198a(17) =131990a(18) =263318a(19) =525974a(20) =1050774a(21) =2100374a(22) =4198550a(23) =8394902a(24) =16785558a(25) =33566870a(26) =67125398a(27) =134242454a(28) =268468374a(29) =536920214