a(n) = -5*a(n-1)-2*a(n-2), n>1 ; a(0)=1, a(1)=-1 .

Terms

a(0) =1a(1) =-1a(2) =3a(3) =-13a(4) =59a(5) =-269a(6) =1227a(7) =-5597a(8) =25531a(9) =-116461a(10) =531243a(11) =-2423293a(12) =11053979a(13) =-50423309a(14) =230008587a(15) =-1049196317a(16) =4785964411a(17) =-21831429421a(18) =99585218283a(19) =-454263232573