a(n) = 3*a(n-1) + 2*a(n-2) for n>1, a(0)=2, a(1)=3.

Terms

a(0) =2a(1) =3a(2) =13a(3) =45a(4) =161a(5) =573a(6) =2041a(7) =7269a(8) =25889a(9) =92205a(10) =328393a(11) =1169589a(12) =4165553a(13) =14835837a(14) =52838617a(15) =188187525a(16) =670239809a(17) =2387094477a(18) =8501763049a(19) =30279478101a(20) =107841960401a(21) =384084837405