a(n) = a(n-1) + 3*a(n-2) -2*a(n-3) - 2*a(n-4), where a(0) = 1, a(1) = -1, a(2) = 1, a(3) = 1.

Terms

a(0) =1a(1) =-1a(2) =1a(3) =1a(4) =4a(5) =7a(6) =15a(7) =26a(8) =49a(9) =83a(10) =148a(11) =247a(12) =427a(13) =706a(14) =1197a(15) =1967a(16) =3292a(17) =5387a(18) =8935a(19) =14578a(20) =24025a(21) =39115a(22) =64164a(23) =104303a(24) =170515a(25) =276866a(26) =451477a(27) =732439a(28) =1192108a(29) =1932739