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

Terms

a(0) =-1a(1) =-2a(2) =3a(3) =-8a(4) =12a(5) =-25a(6) =41a(7) =-79a(8) =136a(9) =-253a(10) =446a(11) =-816a(12) =1455a(13) =-2641a(14) =4735a(15) =-8562a(16) =15391a(17) =-27780a(18) =50000a(19) =-90169a(20) =162389a(21) =-292727a(22) =527336a(23) =-950401a(24) =1712346a(25) =-3085812a(26) =5560103a(27) =-10019381a(28) =18053775a(29) =-32532434