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

Terms

a(0) =2a(1) =2a(2) =16a(3) =44a(4) =184a(5) =632a(6) =2368a(7) =8528a(8) =31264a(9) =113696a(10) =414976a(11) =1512128a(12) =5514112a(13) =20100992a(14) =73286656a(15) =267179264a(16) =974078464a(17) =3551232512a(18) =12946935808a(19) =47201266688a(20) =172084148224a(21) =627375896576