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

Terms

a(0) =-1a(1) =-1a(2) =4a(3) =-11a(4) =29a(5) =-76a(6) =199a(7) =-521a(8) =1364a(9) =-3571a(10) =9349a(11) =-24476a(12) =64079a(13) =-167761a(14) =439204a(15) =-1149851a(16) =3010349a(17) =-7881196a(18) =20633239a(19) =-54018521a(20) =141422324a(21) =-370248451a(22) =969323029a(23) =-2537720636a(24) =6643838879a(25) =-17393796001a(26) =45537549124a(27) =-119218851371a(28) =312119004989a(29) =-817138163596