a(n+3) = 3*(a(n+2) - a(n+1)) + 2*a(n).

Terms

a(0) =1a(1) =2a(2) =2a(3) =2a(4) =4a(5) =10a(6) =22a(7) =44a(8) =86a(9) =170a(10) =340a(11) =682a(12) =1366a(13) =2732a(14) =5462a(15) =10922a(16) =21844a(17) =43690a(18) =87382a(19) =174764a(20) =349526a(21) =699050a(22) =1398100a(23) =2796202a(24) =5592406a(25) =11184812a(26) =22369622a(27) =44739242a(28) =89478484a(29) =178956970