%I #9 Sep 21 2017 03:48:30
%S 0,1,-1,1,-1,1,-1,1,-1,1,-1,-1,2,15,-1,1,-1,1,-1,-1,-1,1,-1,-1,-1,3,
%T -1,1,-1,3,-1,1,-1,1,-1,3,2,-1,-1,15,-1,-1,-1,-1,-1,1,-1,3,-1,-1,-1,1,
%U -1,7,2,-1,2,-1,-1,-1,-1,-1,-1,1,14,1,-1,-1,6,-1,-1
%N 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.
%H Kerry Mitchell, <a href="/A193307/b193307.txt">Table of n, a(n) for n = 0..10000</a>
%H W. J. Gilbert, <a href="https://www.maa.org/programs/faculty-and-departments/classroom-capsules-and-notes/arithmetic-in-complex-bases">Arithmetic in Complex Bases</a>, Mathematics Magazine, Vol. 57, No. 2 (Mar., 1984), pp. 77-81.
%e Decimal 12 is 1100 in binary, which is 2+0i using complex base -1+i. Reversing 1100 gives 0011, or 0+i. Subtracting the original number from the reversed results in -2+i, or 11111 using the complex base. Its reversal is the same, so subtracting them gives 0. Decimal 12 took 2 steps to reach 0, so a(12) = 2.
%Y Cf. A193239 (number of steps needed to reach a palindrome with complex base -1+i).
%Y Cf. 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 the original).
%K sign,base
%O 0,13
%A _Kerry Mitchell_, Jul 22 2011