a(0)=-3, a(1)=4; thereafter a(n) = 2*a(n-1) + a(n-2).

Terms

a(0) =-3a(1) =4a(2) =5a(3) =14a(4) =33a(5) =80a(6) =193a(7) =466a(8) =1125a(9) =2716a(10) =6557a(11) =15830a(12) =38217a(13) =92264a(14) =222745a(15) =537754a(16) =1298253a(17) =3134260a(18) =7566773a(19) =18267806a(20) =44102385a(21) =106472576a(22) =257047537a(23) =620567650a(24) =1498182837a(25) =3616933324a(26) =8732049485a(27) =21081032294a(28) =50894114073a(29) =122869260440