a(1) = 1; a(n) = 1 + a(n-1) + Sum_{k=2..n} a(floor(n/k)).

Terms

a(0) =1a(1) =3a(2) =6a(3) =12a(4) =19a(5) =32a(6) =46a(7) =69a(8) =96a(9) =133a(10) =171a(11) =234a(12) =298a(13) =379a(14) =471a(15) =595a(16) =720a(17) =891a(18) =1063a(19) =1288a(20) =1531a(21) =1815a(22) =2100a(23) =2496a(24) =2900a(25) =3371a(26) =3873a(27) =4479a(28) =5086a(29) =5848