a(n)= +2*a(n-2) +4*a(n-3), n>3.

Terms

a(0) =1a(1) =-6a(2) =-13a(3) =-27a(4) =-50a(5) =-106a(6) =-208a(7) =-412a(8) =-840a(9) =-1656a(10) =-3328a(11) =-6672a(12) =-13280a(13) =-26656a(14) =-53248a(15) =-106432a(16) =-213120a(17) =-425856a(18) =-851968a(19) =-1704192a(20) =-3407360a(21) =-6816256a(22) =-13631488a(23) =-27261952a(24) =-54528000a(25) =-109049856a(26) =-218103808a(27) =-436211712a(28) =-872407040a(29) =-1744838656