a(n) = n for n = 1, 2, 3; for n > 3: a(n) = number of partitions of n into preceding terms.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =6a(5) =10a(6) =12a(7) =17a(8) =21a(9) =29a(10) =34a(11) =47a(12) =55a(13) =71a(14) =84a(15) =107a(16) =124a(17) =156a(18) =180a(19) =221a(20) =256a(21) =310a(22) =355a(23) =428a(24) =488a(25) =578a(26) =660a(27) =775a(28) =879a(29) =1027