Binary Complement Sequences

["Ruud H.G. van Tol" <rvtol@isolution.nl>]

On seqfan, there is a thread about Binary Complement Sequences.

> on any number:
> -multiply by 3
> -find the binary complement (if it is 1001010 in binary,
> the complement is 0110101).


I created this code:

{ bc3(n)= bitneg(n*=3,logint(n,2)); }
{ bc3_seqX(n)= my(x=n,i=0);while(x>0,x=bc3(x);i++);
  print(n," -> ",x," (",i,")"); }
{ bc3_dropX(n)= my(x=n,i=0);until(x<=n,x=bc3(x);i++);
  print(n," -> ",x," (",i,")"); }

Related code on https://oeis.org/wiki/User:Ruud_H.G._van_Tol


? bc3_dropX(22246);
22246 -> 9838 (120796648)
cpu time = 4min, 16,771 ms, real time = 4min, 17,641 ms.

? bc3_seqX(22246);
22246 -> 0 (120796790)
cpu time = 4min, 17,644 ms, real time = 4min, 18,250 ms.


Are there ways to do this faster?


If I inline the bitneg, it becomes:

? bc3_seqX(22246);
22246 -> 0 (120796790)
cpu time = 3min, 39,774 ms, real time = 3min, 40,153 ms.

but I'm of course after a decimation. :)

-- Ruud