a(n) = (3*2^(n-1)-1)*(3*2^n-1).

Terms

a(0) =1a(1) =10a(2) =55a(3) =253a(4) =1081a(5) =4465a(6) =18145a(7) =73153a(8) =293761a(9) =1177345a(10) =4713985a(11) =18865153a(12) =75479041a(13) =301953025a(14) =1207885825a(15) =4831690753a(16) =19327057921a(17) =77308821505a(18) =309236465665