a(n) = ((2^b-1)/phi(n))*Sum_{d|n} Moebius(n/d)*d^(b-1) for b = 6.

Terms

a(0) =63a(1) =1953a(2) =7623a(3) =31248a(4) =49203a(5) =236313a(6) =176463a(7) =499968a(8) =617463a(9) =1525293a(10) =1014615a(11) =3781008a(12) =1949283a(13) =5470353a(14) =5953563a(15) =7999488a(16) =5590683a(17) =19141353a(18) =8666343a(19) =24404688a(20) =21352023a(21) =31453065a(22) =18431343a(23) =60496128a(24) =30751875a(25) =60427773a(26) =50014503a(27) =87525648a(28) =46150083a(29) =184560453