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 A193306 #14 Aug 01 2019 01:13:28 %S A193306 0,1,2,1,4,1,4,1,4,1,4,3,-1,-1,4,1,-1,1,4,-1,-1,1,4,-1,2,11,-1,1,2,11, %T A193306 -1,1,-1,1,12,11,-1,3,2,-1,6,-1,-1,-1,-1,1,12,11,4,-1,-1,1,8,5,-1,3, %U A193306 -1,3,6,-1,4,-1,-1,1,2,1,2,-1,-1,-1,-1,3,2,1,2 %N A193306 Number of 'Reverse and Subtract' steps needed to reach 0, or -1 if never reaches 0, using base -1+i and subtracting the reversed number from original. %H A193306 Kerry Mitchell, <a href="/A193306/b193306.txt">Table of n, a(n) for n = 0..10000</a> %H A193306 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 A193306 Decimal 2 is 10 in binary, which is -1+i using complex base -1+i. Reversing 10 gives 01, or 1+0i. Subtracting the reversed from the original results in -2+i, or 11111 using the complex base. Its reversal is the same, so subtracting them gives 0. Decimal 2 took 2 steps to reach 0, so a(2) = 2. %Y A193306 Cf A193239, number of steps needed to reach a palindrome with complex base -1+i. A193307, Number of 'Reverse and Subtract' steps needed to reach 0, or -1 if never reaches 0, using base -1+i and subtracting the original number from the reversed. %K A193306 sign,base %O A193306 0,3 %A A193306 _Kerry Mitchell_, Jul 22 2011