a(n) = A048141(3*n+1).

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =2a(5) =3a(6) =4a(7) =4a(8) =5a(9) =6a(10) =6a(11) =8a(12) =10a(13) =10a(14) =12a(15) =14a(16) =15a(17) =18a(18) =20a(19) =22a(20) =26a(21) =30a(22) =33a(23) =37a(24) =42a(25) =47a(26) =54a(27) =62a(28) =68a(29) =81