a(n) = a(n-1) + Sum_{k=0..n/3} a(n-3k) with a(0)=1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =4a(6) =7a(7) =11a(8) =16a(9) =26a(10) =41a(11) =62a(12) =98a(13) =154a(14) =237a(15) =371a(16) =581a(17) =901a(18) =1406a(19) =2197a(20) =3418a(21) =5329a(22) =8317a(23) =12956a(24) =20196a(25) =31501a(26) =49096a(27) =76532a(28) =119338a(29) =186029