Number of subsets of {1..n} whose elements have the same number of distinct prime factors.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =9a(5) =17a(6) =18a(7) =34a(8) =66a(9) =130a(10) =132a(11) =260a(12) =264a(13) =520a(14) =528a(15) =544a(16) =1056a(17) =2080a(18) =2112a(19) =4160a(20) =4224a(21) =4352a(22) =4608a(23) =8704a(24) =9216a(25) =17408a(26) =18432a(27) =34816a(28) =36864a(29) =69632