a(n) is the least number with exactly n odd divisors that are <= sqrt(n).

Terms

a(0) =1a(1) =9a(2) =30a(3) =90a(4) =225a(5) =315a(6) =630a(7) =945a(8) =1575a(9) =2835a(10) =4410a(11) =3465a(12) =8190a(13) =6930a(14) =14175a(15) =10395a(16) =27720a(17) =17325a(18) =35910a(19) =31185a(20) =66150a(21) =62370a(22) =99225a(23) =45045a(24) =198450a(25) =90090a(26) =121275a(27) =103950a(28) =207900a(29) =155925