1/4 the number of (n+1) X 5 binary arrays with all 2 X 2 subblock sums the same.

Terms

a(0) =15a(1) =17a(2) =20a(3) =26a(4) =36a(5) =56a(6) =92a(7) =164a(8) =300a(9) =572a(10) =1100a(11) =2156a(12) =4236a(13) =8396a(14) =16652a(15) =33164a(16) =66060a(17) =131852a(18) =263180a(19) =525836a(20) =1050636a(21) =2100236a(22) =4198412a(23) =8394764a(24) =16785420a(25) =33566732a(26) =67125260a(27) =134242316a(28) =268468236a(29) =536920076