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 A023091 #24 Jan 06 2022 18:21:21
%S A023091 0,1359,11688,11883,12903,13029,13359,13449,13590,13599,13659,107583,
%T A023091 108726,111873,116688,116880,116988,118731,118830,118833,119883,
%U A023091 123876,124875,126888,127389,129003,129030,129033,129903,130029,130149,130290
%N A023091 Numbers k such that k and 7*k are anagrams.
%C A023091 All terms are divisible by 3. - _Eric M. Schmidt_, Jul 12 2014
%H A023091 David W. Wilson, <a href="/A023091/b023091.txt">Table of n, a(n) for n = 1..10001</a>
%t A023091 si[n_] := Sort@ IntegerDigits@ n; Flatten@{0, Table[Select[Range[10^d + 2, 2 10^d - 1, 3], si[#] == si[7 #] &], {d, 0, 6}]} (* _Giovanni Resta_, Mar 20 2017 *)
%t A023091 Select[3*Range[0,50000],Sort[IntegerDigits[7 #]]==Sort[IntegerDigits[#]]&] (* _Harvey P. Dale_, Jan 06 2022 *)
%Y A023091 Cf. A023086, A023087, A023088, A023089, A023090, A023092, A023093.
%K A023091 nonn,base
%O A023091 1,2
%A A023091 _David W. Wilson_