a(n) is number of solutions of the equation sigma(x)=10^n.

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =2a(5) =4a(6) =7a(7) =9a(8) =15a(9) =23a(10) =36a(11) =53a(12) =85a(13) =124a(14) =202a(15) =289a(16) =425a(17) =603a(18) =864a(19) =1209a(20) =1699a(21) =2397a(22) =3386a(23) =4665a(24) =6440a(25) =8801a(26) =12101a(27) =16338a(28) =22078a(29) =29565