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

Terms

a(0) =1a(1) =3a(2) =8a(3) =22a(4) =60a(5) =164a(6) =448a(7) =1224a(8) =3344a(9) =9136a(10) =24960a(11) =68192a(12) =186304a(13) =508992a(14) =1390592a(15) =3799168a(16) =10379520a(17) =28357376a(18) =77473792a(19) =211662336a(20) =578272256a(21) =1579869184a(22) =4316282880a(23) =11792304128a(24) =32217174016a(25) =88018956288a(26) =240472260608a(27) =656982433792