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 A109891 #4 Dec 05 2013 19:57:00 %S A109891 0,1,10,16,14,15,13,1011,1017,1037,1027,1014,1013,1028,100143,100135, %T A109891 100145,100134,100103,100195,100137,100227,100114,100128,100194, %U A109891 100107,100307,100277,100413,100345,100429,100215,100444,100237,100433,100335 %N A109891 Least number that requires n steps to reach 0 by repeated application of f: x -> abs(x - reverse(x)). %C A109891 Coincides with A072138 for the first 14 and many later terms. %e A109891 f(16) = 61-16 = 45, f(45) = 54-45 = 9, f(9) = 9-9 = 0. For no k < 16 exactly three steps lead to 0, hence a(3) = 16. %Y A109891 Cf. A072137, A072138, A072141. %K A109891 base,nonn %O A109891 0,3 %A A109891 _Amarnath Murthy_, Jul 13 2005 %E A109891 Edited, corrected and extended by _Klaus Brockhaus_, Jul 14 2005