a(n) = A000120(n) + A001221(n) - 1.

Terms

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