Number of (n+1) X 4 0..2 arrays with all 2 X 2 subblock sums the same.

Terms

a(0) =361a(1) =579a(2) =977a(3) =1887a(4) =3793a(5) =8415a(6) =19217a(7) =47031a(8) =117601a(9) =308799a(10) =822977a(11) =2268807a(12) =6311953a(13) =17963055a(14) =51378737a(15) =149156151a(16) =434130241a(17) =1275821919a(18) =3754108577a(19) =11115905127a(20) =32933734513a(21) =97974065295a(22) =291541674257a(23) =869866334871