a(n) = a(n-2) + a(n-3) + a(n-4) for n>3, a(0)=1, a(1)=a(2)=0, a(3)=2.

Terms

a(0) =1a(1) =0a(2) =0a(3) =2a(4) =1a(5) =2a(6) =3a(7) =5a(8) =6a(9) =10a(10) =14a(11) =21a(12) =30a(13) =45a(14) =65a(15) =96a(16) =140a(17) =206a(18) =301a(19) =442a(20) =647a(21) =949a(22) =1390a(23) =2038a(24) =2986a(25) =4377a(26) =6414a(27) =9401a(28) =13777a(29) =20192