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 A025521 #5 Mar 30 2012 18:35:25 %S A025521 2,2,2,15,15,15,15,41,41,41,41,41,41,41,41,41,41,41,41,41,41,123,123, %T A025521 123,123,123,123,123,123,123,123,123,123,123,123,123,123,123,123,691, %U A025521 691,691,691,691,691,691,691,691,691,691,691,691,691,691,691,691,691,691,691,691 %N A025521 Least k>1 such that complement of first n terms of A022303 repeats beginning at k-th term. %K A025521 nonn %O A025521 1,1 %A A025521 _David W. Wilson_