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 A317027 #17 Feb 04 2020 21:41:47 %S A317027 9,27,324,8000,11025,374544,12723489,432224100,14682895929, %T A317027 498786237504,16944049179225,575598885856164,19553418069930369, %U A317027 664240615491776400,22564627508650467249,766533094678624110084 %N A317027 Perfect powers that appear more than once in the Catalan triangle. %C A317027 Since every integer appears exactly once in the first column of the Catalan triangle, this sequence lists perfect powers that appear in any other column of the triangle. Pell's equation can be used to prove that infinitely many perfect squares appear in this sequence. %H A317027 Nathaniel Benjamin, Grant Fickes, Eugene Fiorini, Edgar Jaramillo Rodriguez, Eric Jovinelly, Tony W. H. Wong, <a href="https://www.emis.de/journals/JIS/VOL22/Fiorini/fiorini3.html">Primes and Perfect Powers in the Catalan Triangle</a>, J. Int. Seq., Vol. 22 (2019), Article 19.7.6. %H A317027 Eric Jovinelly, <a href="/A317027/a317027.txt">Python program</a> %Y A317027 Cf. A009766. %Y A317027 Subsequence of A275586. %K A317027 nonn,more %O A317027 1,1 %A A317027 _Eric Jovinelly_, _Eugene Fiorini_, Jul 19 2018 %E A317027 a(9)-a(16) from _Giovanni Resta_, Jul 29 2018