a(n) = a(n-1) + 4*a(n-2) - 4*a(n-3) for n > 2; a(0)=2, a(1)=3, a(2)=6.

Terms

a(0) =2a(1) =3a(2) =6a(3) =10a(4) =22a(5) =38a(6) =86a(7) =150a(8) =342a(9) =598a(10) =1366a(11) =2390a(12) =5462a(13) =9558a(14) =21846a(15) =38230a(16) =87382a(17) =152918a(18) =349526a(19) =611670a(20) =1398102a(21) =2446678a(22) =5592406a(23) =9786710a(24) =22369622a(25) =39146838a(26) =89478486a(27) =156587350a(28) =357913942a(29) =626349398