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 A307257 #16 Apr 10 2019 22:29:13 %S A307257 0,1,2,3,4,5,155133423353,1535554025003332541,1541322512150022100, %T A307257 14544222532144144105400055,15313352033401001032012412, %U A307257 144510301032554451200342301123415,145033105231511102401034455341005,152142233320210504134120425450055,1435322205115414041210434301130104431115 %N A307257 Numbers k such that k is the substring identical to the most significant digits of its base-6 representation. %C A307257 Numbers k whose base-6 representation begins with the same digits as k itself. %H A307257 Scott R. Shannon, <a href="/A307257/b307257.txt">Table of n, a(n) for n = 1..500</a> %e A307257 155133423353_10 = 155133423353145_6, which also begins with '155133423353'. %o A307257 (PARI) isok(n) = my(vb=digits(n, 6), vd=digits(n)); vd == vector(#vd, k, vb[k]); \\ _Michel Marcus_, Apr 08 2019 %Y A307257 This is a subsequence of A038106. %K A307257 nonn,base %O A307257 1,3 %A A307257 _Scott R. Shannon_, Apr 01 2019