Fibonacci-type sequence based on subtraction: a(0) = 1, a(1) = 2 and a(n) = a(n-2) - a(n-1).

Terms

a(0) =1a(1) =2a(2) =-1a(3) =3a(4) =-4a(5) =7a(6) =-11a(7) =18a(8) =-29a(9) =47a(10) =-76a(11) =123a(12) =-199a(13) =322a(14) =-521a(15) =843a(16) =-1364a(17) =2207a(18) =-3571a(19) =5778a(20) =-9349a(21) =15127a(22) =-24476a(23) =39603a(24) =-64079a(25) =103682a(26) =-167761a(27) =271443a(28) =-439204a(29) =710647