Erroneous version of A002569.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =2a(6) =3a(7) =4a(8) =5a(9) =6a(10) =9a(11) =11a(12) =15a(13) =18a(14) =23a(15) =30a(16) =37a(17) =47a(18) =58a(19) =71a(20) =90