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 A201821 #24 Mar 10 2014 04:24:28 %S A201821 0,1,3,4,13,44,213,344,5344,50213,205344,350213,1350213,4205344, %T A201821 21350213,34205344,221350213,334205344,2221350213,3334205344, %U A201821 52221350213,152221350213,403334205344,5152221350213,55152221350213,155152221350213,400403334205344 %N A201821 Automorphic numbers: n^2 ends with n in base 6 (written in base 6). %D A201821 Albert H. Beiler, Recreations in the theory of numbers, New York, Dover, (2nd ed.) 1966, p. 147. %D A201821 Maurice Kraitchik, Mathematical Recreations, New York, Dover, (2nd ed.) 1953, p. 77. %e A201821 a(3) = (3)_6 = 3 since 3^2 = 9 = (13)_6 ends with 3 in base 6. %e A201821 a(4) = (4)_6 = 4 since 4^2 = 16 = (24)_6 ends with 4 in base 6. %e A201821 a(5) = (13)_6 = 9 since 9^2 = 81 = (213)_6 ends with 13 in base 6. %Y A201821 Cf. A237583 (written in base 10), A003226, A201918, A201919, A201921, A201948. %K A201821 nonn,base %O A201821 1,3 %A A201821 _Martin Renner_, Dec 06 2011 %E A201821 More terms from _Eric M. Schmidt_, Feb 09 2014