a(n) = 3*a(n-1) + 4*a(n-2), with a(0) = 2, a(1) = 6, a(2) = 10.

Terms

a(0) =2a(1) =6a(2) =10a(3) =54a(4) =202a(5) =822a(6) =3274a(7) =13110a(8) =52426a(9) =209718a(10) =838858a(11) =3355446a(12) =13421770a(13) =53687094a(14) =214748362a(15) =858993462a(16) =3435973834a(17) =13743895350a(18) =54975581386a(19) =219902325558a(20) =879609302218