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 A181791 #6 Feb 13 2018 11:03:47 %S A181791 428571428571428571429,571428571428571428572,857142857142857142858, %T A181791 363636363636363636363636363636364,454545454545454545454545454545455, %U A181791 545454545454545454545454545454546,636363636363636363636363636363637 %N A181791 Numbers with pandigital biperiod squares. %D A181791 R. Ondrejka, Problem 1130: Biperiod Squares, Journal of Recreational Mathematics, Vol. 14:4 (1981-82), 299. Solution by F. H. Kierstead, Jr., JRM, Vol. 15:4 (1982-83), 311-312. %Y A181791 Cf. A106497, A181789, A181790. %K A181791 nonn,base %O A181791 1,1 %A A181791 _William Rex Marshall_, Nov 12 2010