a(1)=a(2)=a(3)=1; a(n)=|a(n-2)+a(n-3)|-2*a(n-1).

Terms

a(0) =1a(1) =1a(2) =1a(3) =0a(4) =2a(5) =-3a(6) =8a(7) =-15a(8) =35a(9) =-63a(10) =146a(11) =-264a(12) =611a(13) =-1104a(14) =2555a(15) =-4617a(16) =10685a(17) =-19308a(18) =44684a(19) =-80745a(20) =186866a(21) =-337671a(22) =781463a(23) =-1412121a(24) =3268034a(25) =-5905410a(26) =13666733a(27) =-24696090a(28) =57153503a(29) =-103277649