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

Terms

a(0) =1a(1) =1a(2) =0a(3) =1a(4) =-2a(5) =5a(6) =-12a(7) =29a(8) =-70a(9) =169a(10) =-408a(11) =985a(12) =-2378a(13) =5741a(14) =-13860a(15) =33461a(16) =-80782a(17) =195025a(18) =-470832a(19) =1136689a(20) =-2744210a(21) =6625109a(22) =-15994428a(23) =38613965a(24) =-93222358a(25) =225058681a(26) =-543339720a(27) =1311738121a(28) =-3166815962a(29) =7645370045