Number of (n+1) X 7 0..2 arrays with every 2 X 2 subblock summing to 4.

Terms

a(0) =2445a(1) =2967a(2) =4029a(3) =6207a(4) =10725a(5) =20247a(6) =40749a(7) =86127a(8) =190005a(9) =437127a(10) =1049469a(11) =2628447a(12) =6849285a(13) =18479607a(14) =51306189a(15) =145657167a(16) =420452565a(17) =1228323687a(18) =3618906909a(19) =10724596287a(20) =31909543845a(21) =95200145367a(22) =284543467629