a(n) = 2*a(n-1) + 2*a(n-2) - 2*a(n-3) with a(0)=3, a(1)=2, a(3)=8.

Terms

a(0) =3a(1) =2a(2) =8a(3) =14a(4) =40a(5) =92a(6) =236a(7) =576a(8) =1440a(9) =3560a(10) =8848a(11) =21936a(12) =54448a(13) =135072a(14) =335168a(15) =831584a(16) =2063360a(17) =5119552a(18) =12702656a(19) =31517696a(20) =78201600a(21) =194033280a(22) =481434368a(23) =1194532096a(24) =2963866368a(25) =7353928192