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 A113917 #18 Mar 25 2023 22:20:29
%S A113917 2,1849,2,266423227914725931,3100840870711697060720215047,
%T A113917 845486430620513036335402848567278325780455810752216401,4
%N A113917 Maximal element of Image^inf({ 2 }) under repeated base-n zero-split squaring.
%C A113917 Define f_b(x) to be the set of base b numbers left after splitting x^2 at its zero digits and Image_b(S) = union_{x in S}{ { x } union f_b(S) }, then a(n) = max(Image_n^inf({ 2 }))
%C A113917 Conjecture: a(n) is finite for all n.
%H A113917 Hugo van der Sanden, <a href="https://github.com/hvds/seq/tree/master/zerofree">Perl and C implementations</a>, Feb 03 2015
%e A113917 f_10(29648) = { 4, 39, 879 } since 29648^2 = 879003904;
%e A113917 a(8) = 4 since Image_8({ 2 }) = { 2, 4 } and f_8({ 2, 4 }) = { 2, 4 } and max({ 2, 4 }) is 4.
%Y A113917 Cf. A113918.
%K A113917 nonn,hard
%O A113917 2,1
%A A113917 _Hugo van der Sanden_ extending a suggestion from _David W. Wilson_, Jan 31 2006
%E A113917 Corrected by _Hugo van der Sanden_, Feb 03 2015