a(n) = PrimePi(A246033(n)) (where PrimePi = A000720).

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =15a(5) =21a(6) =30a(7) =46a(8) =61a(9) =91a(10) =121a(11) =154a(12) =189a(13) =217a(14) =258a(15) =409a(16) =548a(17) =590a(18) =775a(19) =832a(20) =906a(21) =1227a(22) =1270a(23) =1570a(24) =1847a(25) =2116a(26) =2688a(27) =3607a(28) =3714a(29) =3990