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

Terms

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