The sequence M(n) in A022906.

Terms

a(0) =0a(1) =2a(2) =1a(3) =1a(4) =2a(5) =3a(6) =4a(7) =4a(8) =3a(9) =4a(10) =5a(11) =6a(12) =7a(13) =7a(14) =6a(15) =7a(16) =8a(17) =9a(18) =10a(19) =9a(20) =9a(21) =10a(22) =11a(23) =12a(24) =12a(25) =12a(26) =11a(27) =12a(28) =14a(29) =15