a(n) = 4*a(n-1)-2*a(n-2)-3*a(n-3)+2*a(n-4), n>5.

Terms

a(0) =3a(1) =3a(2) =10a(3) =29a(4) =94a(5) =292a(6) =913a(7) =2844a(8) =8862a(9) =27605a(10) =85990a(11) =267852a(12) =834337a(13) =2598884a(14) =8095286a(15) =25216069a(16) =78545726a(17) =244662676a(18) =762101617a(19) =2373876076a(20) =7394404494a(21) =23032886325a(22) =71745311318a(23) =223480011292a(24) =696119572545