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 A201921 #13 Mar 23 2020 17:32:01 %S A201921 0,1,6,10,100,126,1000,2376,4375,46251,156250,603126,3640626,7750000, %T A201921 19140625,151718751,835156251,1727734375,5960937501,32482421875, %U A201921 236621093751,340029296875,8413134765625,60784912109376,68961425781250,709516601562501,1236678466796875 %N A201921 Automorphic numbers: n^2 ends with n in base 15 (written in base 10). %H A201921 Eric M. Schmidt, <a href="/A201921/b201921.txt">Table of n, a(n) for n = 1..1000</a> %e A201921 a(3) = 6 = (6)_15 since 6^2 = 36 = (26)_15 ends with 6 in base 15. %e A201921 a(4) = 10 = (A)_15 since 10^2 = 100 = (6A)_15 ends with A in base 15. %e A201921 a(5) = 100 = (6A)_15 since 100^2 = 10000 = (2E6A)_15 ends with 6A in base 15. %o A201921 (Sage) # See A003226. - _Eric M. Schmidt_, Feb 09 2014 %Y A201921 Cf. A003226, A201821, A201918, A201919, A201948, A237583. %K A201921 nonn,base %O A201921 1,3 %A A201921 _Martin Renner_, Dec 06 2011 %E A201921 More terms from _Eric M. Schmidt_, Feb 09 2014