Erroneous version of A173380.

Terms

a(0) =1a(1) =4a(2) =12a(3) =28a(4) =68a(5) =164a(6) =396a(7) =940a(8) =2244a(9) =5324a(10) =12668a(11) =29940a(12) =71012a(13) =167468a(14) =396204