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 A193886 #40 Sep 07 2020 17:25:49
%S A193886 6,11,15,24,54,60,66,81,96,110,111,123,135,144,150,165,216,225,240,
%T A193886 303,352,375,384,396,477,528,540,600,660,666,711,717,738,792,810,813,
%U A193886 960,1056,1100,1110,1111,1230,1350,1440,1500,1536,1650,1665,1728,1818,1845,2043,2079
%N A193886 Numbers n such that the decimal form of the period of 1/n is semiprime (omit any trailing zeros from the period).
%C A193886 The sequence is infinite: if n is in the sequence, then n*10^m, m = 1,2,... are in the sequence.
%C A193886 The subsequence of semiprimes k such that the decimal form of the period of 1/k is semiprime begins: 6, 15, 111, 123, 303, 717, 813, 1111. - _Jonathan Vos Post_, Oct 22 2011
%F A193886 { n : A060284(n) in {A001358} }.
%e A193886 54 is in the sequence because 1/54 = 0.01851851851851... and 185 = 5*37 is semiprime.
%e A193886 110 is in the sequence because 1/110 = 0.009090909090..., with period "90", and 9 is a semiprime. - _Harvey P. Dale_ and _N. J. A. Sloane_, Sep 07 2020
%t A193886 Reap[Do[p=RealDigits[1/k][[1,-1]];If[Head[p]===List,While[p[[-1]]==0,p=Most[p]];If[PrimeOmega[FromDigits[p]]==2,Sow[k]]],{k,120}]][[2,1]]
%Y A193886 Cf. A001358, A060284.
%K A193886 nonn,base,hard
%O A193886 1,1
%A A193886 _Michel Lagneau_, Aug 07 2011
%E A193886 a(12)-a(53) from _Alois P. Heinz_, Aug 09 2011