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

Terms

a(0) =1a(1) =2a(2) =3a(3) =2a(4) =0a(5) =-3a(6) =-5a(7) =-5a(8) =-2a(9) =3a(10) =8a(11) =10a(12) =7a(13) =-1a(14) =-11a(15) =-18a(16) =-17a(17) =-6a(18) =12a(19) =29a(20) =35a(21) =23a(22) =-6a(23) =-41a(24) =-64a(25) =-58a(26) =-17a(27) =47a(28) =105a(29) =122