a(n) = Sum_{d|n} Moebius(n/d)*d^(b-1)/phi(n) for b = 7.

Terms

a(0) =1a(1) =63a(2) =364a(3) =2016a(4) =3906a(5) =22932a(6) =19608a(7) =64512a(8) =88452a(9) =246078a(10) =177156a(11) =733824a(12) =402234a(13) =1235304a(14) =1421784a(15) =2064384a(16) =1508598a(17) =5572476a(18) =2613660a(19) =7874496a(20) =7137312a(21) =11160828a(22) =6728904a(23) =23482368a(24) =12206250a(25) =25340742a(26) =21493836a(27) =39529728a(28) =21243690a(29) =89572392