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 A031213 #13 Feb 16 2025 08:32:36 %S A031213 1,1,17,123,17,17,123,123,123,123,1,17,123,17,123,123,123,81,81,123, %T A031213 17,123,123,123,123,123,123,123,123,123,123,17,123,123,123,123,123,81, %U A031213 17,123,17,123,123,123,123,123,7,123,123,123,17,123,123,123,123 %N A031213 Periods of sum of 10th powers of digits iterated until the sequence becomes periodic. %H A031213 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Digitaddition.html">Digitaddition</a> %K A031213 nonn,base %O A031213 0,3 %A A031213 _Eric W. Weisstein_ %E A031213 Missing a(0)=1 inserted by _Sean A. Irvine_, Apr 15 2020