a(0)=-4, a(1)=5; thereafter a(n) = 2*a(n-1) + a(n-2).

Terms

a(0) =-4a(1) =5a(2) =6a(3) =17a(4) =40a(5) =97a(6) =234a(7) =565a(8) =1364a(9) =3293a(10) =7950a(11) =19193a(12) =46336a(13) =111865a(14) =270066a(15) =651997a(16) =1574060a(17) =3800117a(18) =9174294a(19) =22148705a(20) =53471704a(21) =129092113a(22) =311655930a(23) =752403973a(24) =1816463876a(25) =4385331725a(26) =10587127326a(27) =25559586377a(28) =61706300080a(29) =148972186537