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 A193239 #13 Sep 26 2017 10:58:49 %S A193239 0,0,1,0,1,0,-1,0,1,0,1,6,1,6,1,0,1,0,1,4,-1,0,-1,-1,1,4,-1,0,-1,-1,5, %T A193239 0,1,0,1,6,1,-1,1,-1,1,-1,1,-1,-1,0,7,-1,1,6,7,0,1,-1,1,2,1,-1,1,2,7, %U A193239 -1,-1,0,1,0,1,-1,1,-1,1,-1,3,0,-1,-1,9,2,1 %N A193239 Number of "Reverse and Add" steps needed to reach a palindrome using the complex base -1+i, or -1 if a palindrome is never reached. %C A193239 N is converted to its binary representation before iterating. %H A193239 Kerry Mitchell, <a href="/A193239/b193239.txt">Table of n, a(n) for n = 0..10000</a> %H A193239 W. J. Gilbert, <a href="http://www.jstor.org/stable/2689587">Arithmetic in Complex Bases</a>, Mathematics Magazine, Vol. 57, No. 2 (Mar., 1984), pp. 77-81. %e A193239 Decimal 2 is 10 in binary, which is -1+i using complex base -1+i. Reversing 10 gives 01, or 1+0i. Adding both results in 0+i, or 11 using the complex base, which is a palindrome. Decimal 2 took 1 step to reach a palindrome, so a(2) = 1. %Y A193239 Cf. A033665 gives the steps to reach a palindrome in base 10. %K A193239 base,sign %O A193239 0,12 %A A193239 _Kerry Mitchell_, Jul 19 2011