a(n) = 3*a(n-1) + 2*a(n-2), with a(0)=2, a(1)=7.

Terms

a(0) =2a(1) =7a(2) =25a(3) =89a(4) =317a(5) =1129a(6) =4021a(7) =14321a(8) =51005a(9) =181657a(10) =646981a(11) =2304257a(12) =8206733a(13) =29228713a(14) =104099605a(15) =370756241a(16) =1320467933a(17) =4702916281a(18) =16749684709a(19) =59654886689a(20) =212464029485a(21) =756701861833