Horadam sequence (0,1,4,2).

Terms

a(0) =0a(1) =1a(2) =2a(3) =8a(4) =24a(5) =80a(6) =256a(7) =832a(8) =2688a(9) =8704a(10) =28160a(11) =91136a(12) =294912a(13) =954368a(14) =3088384a(15) =9994240a(16) =32342016a(17) =104660992a(18) =338690048a(19) =1096024064a(20) =3546808320a(21) =11477712896a(22) =37142659072a(23) =120196169728a(24) =388962975744