Number of compositions (p_1, p_2, p_3, ...) of n with 1 <= p_i <= i for all i.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =6a(6) =11a(7) =21a(8) =41a(9) =80a(10) =157a(11) =310a(12) =614a(13) =1218a(14) =2421a(15) =4819a(16) =9602a(17) =19147a(18) =38204a(19) =76266a(20) =152307a(21) =304256a(22) =607941a(23) =1214970a(24) =2428482a(25) =4854630a(26) =9705518a(27) =19405030a(28) =38800412a(29) =77585314