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 A072018 #13 Aug 27 2024 09:16:43 %S A072018 4899999987,4989999897,4999889997,4999997889,5889998997,5889999969, %T A072018 5898989997,5898998988,5899899789,5899979979,5899987998,5899989699, %U A072018 5899996989,5979999879,5988899997,5988998898,5989889979,5989897998 %N A072018 Numbers k for which gcd(k, reverse(k)) = 243 = 3^5. %H A072018 Sean A. Irvine, <a href="/A072018/b072018.txt">Table of n, a(n) for n = 1..1000</a> %e A072018 k = 4899999987 = 3*3*3*3*3*157*128437 and reverse(k) = 78999999984 = 2*2*2*2*3*3*3*3*3*3*2031893, gcd = 243. Numerous but not all solutions are obtained by inserting strings of 9's between digits of A071016. Further such regular transformations exist. %Y A072018 Cf. A004086, A055483, A069554, A071686, A072005, A072016. %K A072018 nonn,base %O A072018 1,1 %A A072018 _Labos Elemer_, Jun 05 2002