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 A173931 #5 Mar 30 2012 17:22:55
%S A173931 4,10,13,28,40,82,91,121,146,182,205,244,328,364,386,656,671,730,757,
%T A173931 820,949,1036,1093,1342,1640,2044,2188,2362,2555,2644,2684,2812,2920,
%U A173931 3280,3640,3796,3851,4088,4561,4745,5110,6176,6562,6643,7381,7592,7913
%N A173931 Primitive numbers k such that m/k is in the Cantor set for some m.
%C A173931 Primitive means no k is a multiple of 3. This is sequence A054591 without the multiples of 3. Sequence A173793 is a subsequence. Sequence A173932 gives the least m such for each k. Sequence A173933 gives the number of m < k/2 such that m/k is in the Cantor set. Irregular triangle A173934 gives a row of m values for each k.
%C A173931 The remaining terms <10000 are 9139, 9490, 9841.
%C A173931 It is assumed that gcd(m,k) = 1.
%H A173931 T. D. Noe, <a href="/A173931/b173931.txt">Table of n, a(n) for n=1..185</a>
%t A173931 InCantorQ[m_, n_] := !MemberQ[Union[Flatten[RealDigits[m/n,3][[1]]]], 1]; cantor=Reap[Do[If[Mod[n,3] > 0, s=Select[Range[Ceiling[n/2]], GCD[n,# ]==1 && InCantorQ[ #,n] &]; If[s != {}, Sow[{n, s}]]], {n,10000}]][[2,1]]; First[Transpose[cantor]]
%K A173931 nonn
%O A173931 1,1
%A A173931 _T. D. Noe_, Mar 03 2010