This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A086564 #21 Jun 18 2023 15:56:31
%S A086564 0,4,3,11,9,36,15,33,39,69,63,45,171,117,243,105,150,135,165,255,231,
%T A086564 210
%N A086564 Smallest k such that 10^k + 1 has n distinct prime divisors.
%C A086564 a(27) = 330; a(28) = 315; a(23) >= 347. - _Max Alekseyev_, Jun 18 2023
%C A086564 a(23) <= 385. - _Jon E. Schoenfield_, Jun 18 2023
%F A086564 a(n) = log_10(A086563(n) - 1).
%e A086564 a(5) = 9 = log_10(1000000001 - 1).
%t A086564 Module[{nn=70,pn},pn=PrimeNu/@(10^Range[0,nn]+1);Flatten[Table[Position[pn,n,1,1],{n,12}]]]-1 (* _Harvey P. Dale_, Jun 10 2023 *)
%Y A086564 Smallest inverse of A119704.
%Y A086564 Cf. A086563.
%K A086564 more,nonn
%O A086564 1,2
%A A086564 _Amarnath Murthy_, Aug 31 2003
%E A086564 More terms from _Sascha Kurz_, Sep 22 2003
%E A086564 a(10)-a(12) from _David Wasserman_, Mar 28 2005
%E A086564 a(13)-a(22) from _Max Alekseyev_, Apr 27 2010