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 A105311 #11 Feb 16 2025 08:32:57 %S A105311 1,1212,123123123,1234123412341234,1234512345123451234512345, %T A105311 123456123456123456123456123456123456, %U A105311 1234567123456712345671234567123456712345671234567,1234567812345678123456781234567812345678123456781234567812345678,123456789123456789123456789123456789123456789123456789123456789123456789123456789 %N A105311 a(n) = n concatenations of numbers from 1 to n, concatenated. %D A105311 F. Smarandache, "Properties of the numbers", Univ. of Craiova Archives, 1975; Arizona State University Special Collections, Tempe, AZ. %H A105311 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SmarandacheSequences.html">Smarandache Sequences</a>. %Y A105311 Cf. A098129, A000461. %K A105311 easy,nonn,base %O A105311 1,2 %A A105311 _Alexandre Wajnberg_, Apr 25 2005 %E A105311 a(5) corrected and more terms from _Georg Fischer_, Nov 13 2024